Any*{Converter,Importer}: clean up ancient log redirection in tests.

It's usually just `out` nowadays, and it's restricted to the smallest
possible scope to not hide errors coming from elsewhere.

src/MagnumPlugins/AnyAudioImporter/Test/AnyAudioImporterTest.cpp

@@ -135,13 +135,12 @@ void AnyImporterTest::detect() {
 }
 
 void AnyImporterTest::unknown() {
-    std::ostringstream output;
-    Error redirectError{&output};
-
     Containers::Pointer<AbstractImporter> importer = _manager.instantiate("AnyAudioImporter");
-    CORRADE_VERIFY(!importer->openFile("sound.mid"));
 
-    CORRADE_COMPARE(output.str(), "Audio::AnyImporter::openFile(): cannot determine the format of sound.mid\n");
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!importer->openFile("sound.mid"));
+    CORRADE_COMPARE(out.str(), "Audio::AnyImporter::openFile(): cannot determine the format of sound.mid\n");
 }
 
 void AnyImporterTest::propagateConfiguration() {

src/MagnumPlugins/AnyImageImporter/Test/AnyImageImporterTest.cpp

@@ -311,36 +311,33 @@ void AnyImageImporterTest::detect() {
 }
 
 void AnyImageImporterTest::unknownExtension() {
-    std::ostringstream output;
-    Error redirectError{&output};
-
     Containers::Pointer<AbstractImporter> importer = _manager.instantiate("AnyImageImporter");
-    CORRADE_VERIFY(!importer->openFile("image.xcf"));
 
-    CORRADE_COMPARE(output.str(), "Trade::AnyImageImporter::openFile(): cannot determine the format of image.xcf\n");
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!importer->openFile("image.xcf"));
+    CORRADE_COMPARE(out.str(), "Trade::AnyImageImporter::openFile(): cannot determine the format of image.xcf\n");
 }
 
 void AnyImageImporterTest::unknownSignature() {
     auto&& data = DetectUnknownData[testCaseInstanceId()];
     setTestCaseDescription(data.name);
 
-    std::ostringstream output;
-    Error redirectError{&output};
-
     Containers::Pointer<AbstractImporter> importer = _manager.instantiate("AnyImageImporter");
-    CORRADE_VERIFY(!importer->openData(data.data));
 
-    CORRADE_COMPARE(output.str(), Utility::formatString("Trade::AnyImageImporter::openData(): cannot determine the format from signature 0x{}\n", data.signature));
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!importer->openData(data.data));
+    CORRADE_COMPARE(out.str(), Utility::formatString("Trade::AnyImageImporter::openData(): cannot determine the format from signature 0x{}\n", data.signature));
 }
 
 void AnyImageImporterTest::emptyData() {
-    std::ostringstream output;
-    Error redirectError{&output};
-
     Containers::Pointer<AbstractImporter> importer = _manager.instantiate("AnyImageImporter");
-    CORRADE_VERIFY(!importer->openData(nullptr));
 
-    CORRADE_COMPARE(output.str(), "Trade::AnyImageImporter::openData(): file is empty\n");
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!importer->openData(nullptr));
+    CORRADE_COMPARE(out.str(), "Trade::AnyImageImporter::openData(): file is empty\n");
 }
 
 void AnyImageImporterTest::propagateFlags() {

src/MagnumPlugins/AnySceneConverter/Test/AnySceneConverterTest.cpp

@@ -144,13 +144,12 @@ void AnySceneConverterTest::detect() {
 }
 
 void AnySceneConverterTest::unknown() {
-    std::ostringstream output;
-    Error redirectError{&output};
-
     Containers::Pointer<AbstractSceneConverter> converter = _manager.instantiate("AnySceneConverter");
-    CORRADE_VERIFY(!converter->convertToFile(MeshData{MeshPrimitive::Triangles, 0}, "mesh.obj"));
 
-    CORRADE_COMPARE(output.str(), "Trade::AnySceneConverter::convertToFile(): cannot determine the format of mesh.obj\n");
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!converter->convertToFile(MeshData{MeshPrimitive::Triangles, 0}, "mesh.obj"));
+    CORRADE_COMPARE(out.str(), "Trade::AnySceneConverter::convertToFile(): cannot determine the format of mesh.obj\n");
 }
 
 void AnySceneConverterTest::propagateFlags() {

src/MagnumPlugins/AnySceneImporter/Test/AnySceneImporterTest.cpp

@@ -196,13 +196,12 @@ void AnySceneImporterTest::detect() {
 }
 
 void AnySceneImporterTest::unknown() {
-    std::ostringstream output;
-    Error redirectError{&output};
-
     Containers::Pointer<AbstractImporter> importer = _manager.instantiate("AnySceneImporter");
-    CORRADE_VERIFY(!importer->openFile("mesh.wtf"));
 
-    CORRADE_COMPARE(output.str(), "Trade::AnySceneImporter::openFile(): cannot determine the format of mesh.wtf\n");
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!importer->openFile("mesh.wtf"));
+    CORRADE_COMPARE(out.str(), "Trade::AnySceneImporter::openFile(): cannot determine the format of mesh.wtf\n");
 }
 
 void AnySceneImporterTest::propagateFlags() {