Require time before monkey-patching it

Same as #12710 but for the time module this time. This time it should
fix the Active Model test suite in isolation avoiding a TypeError to
be raised about the superclass of the DateTime object.

activesupport/lib/active_support/core_ext/object/json.rb

@@ -1,6 +1,7 @@
 # Hack to load json gem first so we can overwrite its to_json.
 require 'json'
 require 'bigdecimal'
+require 'time'
 
 # The JSON gem adds a few modules to Ruby core classes containing :to_json definition, overwriting
 # their default behavior. That said, we need to define the basic to_json method in all of them,

activesupport/lib/active_support/json/encoding.rb

@@ -7,7 +7,6 @@
 require 'active_support/core_ext/hash/except'
 require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/object/instance_variables'
-require 'time'
 require 'active_support/core_ext/time/conversions'
 require 'active_support/core_ext/date_time/conversions'
 require 'active_support/core_ext/date/conversions'