Lint/UnusedMethodArgument autocorrect renames unused keywords

[anthonybishopric]

Running rubocop -a on a file containing

def foo(a: 1, b: 2)

where b is unused with rename b to _b. This is fine for ordinal'd arguments, but keyword arguments may be passed by clients, resulting in ArgumentError: unknown keyword: b. Keyword arguments should never be renamed by the auto corrector

[yujinakayama]

Thank for the report. I'll take a look.