Rewrite GrammarRule.token() to only check content.

10_compiler_i_syntax_analysis/jackcompiler/syntax/parser.py
	-There isn't currently a use-case for verifying the type of a
	token along with its content in grammar rules. Thus, rewrite
	`GrammarRule.token()` to accept only a string argument, rather
	than a full Token tuple; it's now similar to
	`GrammarRule.token_type()`.