[Fix #790] Make smaller replace in MethodDefParentheses autocorrect

Replacing the entire method definition gives the error "#<Parser::Source::Range ...> spans more than one line" if there is another auto-correction within that method. So we replace the smallest ranges we can.
Merge pull request #792 from jonas054/fix_autocorrect_interference

[Fix #790] Make smaller replace in MethodDefParentheses autocorrect