package/ci: properly enable Tga{Importer,ImageConverter} on Windows GLES.

The way it is now it doesn't make sense (as MagnumFont[Converter]
depends on these), and thus the backwards compatibility options don't
work.

package/ci/appveyor-desktop-gles.bat

@@ -45,8 +45,8 @@ cmake .. ^
     -DWITH_MAGNUMFONT=ON ^
     -DWITH_MAGNUMFONTCONVERTER=ON ^
     -DWITH_OBJIMPORTER=OFF ^
-    -DWITH_TGAIMAGECONVERTER=OFF ^
+    -DWITH_TGAIMAGECONVERTER=ON ^
-    -DWITH_TGAIMPORTER=OFF ^
+    -DWITH_TGAIMPORTER=ON ^
     -DWITH_WAVAUDIOIMPORTER=OFF ^
     -DWITH_DISTANCEFIELDCONVERTER=OFF ^
     -DWITH_FONTCONVERTER=OFF ^