Remove (deprecated) isOpaque parameter to SkSL shaders (#31242)
Remove (deprecated) isOpaque parameter to SkSL shaders (#31242)

SkSL now determines this automatically, so the isOpaque paramter is
going away. The local matrix parameter now has a nullptr default.
devoncarew/engine,flutter/engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,rmacnak-google/engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,jason-simmons/flutter_engine,jason-simmons/flutter_engine,jason-simmons/flutter_engine,jason-simmons/flutter_engine,devoncarew/engine,devoncarew/engine,devoncarew/engine,flutter/engine,chinmaygarde/flutter_engine,rmacnak-google/engine,chinmaygarde/flutter_engine,rmacnak-google/engine,rmacnak-google/engine,devoncarew/engine,rmacnak-google/engine,devoncarew/engine,rmacnak-google/engine,devoncarew/engine,flutter/engine,jason-simmons/flutter_engine,flutter/engine,chinmaygarde/flutter_engine,rmacnak-google/engine,chinmaygarde/flutter_engine,chinmaygarde/flutter_engine,flutter/engine,flutter/engine,jason-simmons/flutter_engine,flutter/engine,flutter/engine