Remove highlighting for "string" lowercase literal

Author: facchinm

build/shared/lib/keywords.txt

@@ -76,7 +76,6 @@ signed	LITERAL1		RESERVED_WORD_2
 static	LITERAL1	Static	RESERVED_WORD_2
 volatile	LITERAL1	Volatile	RESERVED_WORD_2
 String	LITERAL1	String	RESERVED_WORD_2
-string	LITERAL1	string	RESERVED_WORD_2
 void	LITERAL1	Void	RESERVED_WORD_2
 true	LITERAL1		LITERAL_BOOLEAN
 unsigned	LITERAL1		RESERVED_WORD_2