GDScript completion: Handle quote style ad-hoc to remove editor dependency

`core` and `scene` shouldn't depend on `editor`, so they can't query this style
setting in `get_argument_options`. But we can handle it after the fact in
GDScript's completion code.

Also cleans up a couple extra unused invalid includes in `core`.

core/os/os.cpp

@@ -36,7 +36,6 @@
 #include "core/io/file_access.h"
 #include "core/os/midi_driver.h"
 #include "core/version_generated.gen.h"
-#include "servers/audio_server.h"
 
 #include <stdarg.h>