CMake: embarrassing typo prevented ObjImporter from working in subprojects.

I am on a roll today!

doc/changelog.dox

@@ -128,6 +128,9 @@ See also:
     using a static build of SDL2 on Linux
 -   `FindSDL2.cmake` is now able to properly find a debug build of SDL, which
     enables Vcpkg to properly copy all dependency DLLs on Windows
+-   @ref Magnum::ObjImporter "ObjImporter" didn't work with CMake subprojects
+    due to an embarrassing typo (see
+    [mosra/magnum#259](https://github.com/mosra/magnum/issues/259))
 
 @subsection changelog-latest-bugfixes Bug fixes
 

src/MagnumPlugins/ObjImporter/CMakeLists.txt

@@ -60,4 +60,4 @@ if(BUILD_TESTS)
 endif()
 
 # Magnum ObjImporter library for superprojects
-add_library(Magnum:::ObjImporter ALIAS ObjImporter)
+add_library(Magnum::ObjImporter ALIAS ObjImporter)