* Undo pull request #16742 while keeping fixed indentation on ccShader_UI_Gray.frag * Removed unnecessary whitespace * Switched implementation to C++11 string literal Thanks to stevetranby for the suggestion
* Removes unused 'return' letter in builtin shader. * Updates indention of ccShader_UI_Gray.frag.
Ticket: https://github.com/cocos2d/cocos2d-x/issues/14378