Fix Performance/DeletePrefix cop (#24796)

app/lib/activitypub/case_transform.rb

@@ -13,7 +13,7 @@ module ActivityPub::CaseTransform
       when Symbol then camel_lower(value.to_s).to_sym
       when String
         camel_lower_cache[value] ||= if value.start_with?('_:')
-                                       "_:#{value.gsub(/\A_:/, '').underscore.camelize(:lower)}"
+                                       "_:#{value.delete_prefix('_:').underscore.camelize(:lower)}"
                                      else
                                        value.underscore.camelize(:lower)
                                      end

app/lib/permalink_redirector.rb

@@ -52,7 +52,7 @@ class PermalinkRedirector
   end
 
   def path_segments
-    @path_segments ||= @path.gsub(/\A\//, '').split('/')
+    @path_segments ||= @path.delete_prefix('/').split('/')
   end
 
   def find_status_url_by_id(id)

app/lib/webfinger_resource.rb

@@ -57,7 +57,7 @@ class WebfingerResource
   end
 
   def resource_without_acct_string
-    resource.gsub(/\Aacct:/, '')
+    resource.delete_prefix('acct:')
   end
 
   def local_username