Remove custom patterns from .gitignore

.gitignore

@@ -1,3 +1,8 @@
+# Don't add any custom patterns for platform-specific files like .DS_Store
+# or generated by custom development tools like .vscode or .idea that don't
+# affect other developers. Instead add those custom patterns to your global
+# .gitignore file.
+
 *.diff
 *.log
 *.o
@@ -38,7 +43,6 @@ src/test/test_data
 src/test/golden_buffers/*.actual
 
 res/qrc_mixxx.cc
-res/developer_skins
 
 *.wixobj
 *.wixpdb
@@ -58,6 +62,4 @@ lib/*/lib/*.lib
 
 lib/qtscript-bytearray/*.cc
 
-.idea
-*.vscode
 compile_commands.json