Change `gsub` to `tr` where possible

actionview/test/template/test_case_test.rb

@@ -155,7 +155,7 @@ class ViewAssignsTest < ActionView::TestCase
     test "view_assigns excludes internal ivars" do
       INTERNAL_IVARS.each do |ivar|
         assert defined?(ivar), "expected #{ivar} to be defined"
-        assert !view_assigns.keys.include?(ivar.to_s.sub('@', '').to_sym), "expected #{ivar} to be excluded from view_assigns"
+        assert !view_assigns.keys.include?(ivar.to_s.tr('@', '').to_sym), "expected #{ivar} to be excluded from view_assigns"
       end
     end
   end

activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb

@@ -11,7 +11,7 @@ def initialize(lhs_class, rhs_class_name)
         end
 
         def join_table
-          @join_table ||= [@lhs_class.table_name, klass.table_name].sort.join("\0").gsub(/^(.*[._])(.+)\0\1(.+)/, '\1\2_\3').gsub("\0", "_")
+          @join_table ||= [@lhs_class.table_name, klass.table_name].sort.join("\0").gsub(/^(.*[._])(.+)\0\1(.+)/, '\1\2_\3').tr("\0", "_")
         end
 
         private

activerecord/lib/active_record/model_schema.rb

@@ -63,7 +63,7 @@ module ModelSchema
     #   records, artists => artists_records
     #   music_artists, music_records => music_artists_records
     def self.derive_join_table_name(first_table, second_table) # :nodoc:
-      [first_table.to_s, second_table.to_s].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').gsub("\0", "_")
+      [first_table.to_s, second_table.to_s].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').tr("\0", "_")
     end
 
     module ClassMethods

activesupport/lib/active_support/values/time_zone.rb

@@ -184,7 +184,7 @@ class TimeZone
     }
 
     UTC_OFFSET_WITH_COLON = '%s%02d:%02d'
-    UTC_OFFSET_WITHOUT_COLON = UTC_OFFSET_WITH_COLON.sub(':', '')
+    UTC_OFFSET_WITHOUT_COLON = UTC_OFFSET_WITH_COLON.tr(':', '')
 
     @lazy_zones_map = ThreadSafe::Cache.new