Update the `Performance/RegexpMatch` cop by koic · Pull Request #3833 · rubocop/rubocop

Follow up to #3824. Cc: @pocke Thanks. Benchmark `Regexp#===` is also slower than `Regexp#match?`. % ruby -v ruby 2.4.0p0 (2016-12-24 revision 57164) [x86_64-darwin13] % cat regexp_match.rb requir...