Fix Performance/StartWith cop (#24818)

.rubocop_todo.yml

@@ -255,12 +255,6 @@ Performance/MapCompact:
     - 'db/migrate/20200407202420_migrate_unavailable_inboxes.rb'
     - 'spec/presenters/status_relationships_presenter_spec.rb'
 
-# This cop supports unsafe autocorrection (--autocorrect-all).
-# Configuration parameters: SafeMultiline.
-Performance/StartWith:
-  Exclude:
-    - 'app/lib/extractor.rb'
-
 # This cop supports unsafe autocorrection (--autocorrect-all).
 Performance/UnfreezeString:
   Exclude:

app/lib/extractor.rb

@@ -64,7 +64,7 @@ module Extractor
       end_position   = match_data.char_end(1)
       after          = ::Regexp.last_match.post_match
 
-      if %r{\A://}.match?(after)
+      if after.start_with?('://')
         hash_text.match(/(.+)(https?\Z)/) do |matched|
           hash_text     = matched[1]
           end_position -= matched[2].codepoint_length