[rails6][evm_spec_helper.rb] require 'rspec/mocks'

This doesn't seem to be included by default anymore, as the following
error was generated without it:

    An error occurred while loading spec_helper.
    Failure/Error: extend RSpec::Mocks::ExampleMethods

    NameError:
      uninitialized constant RSpec::Mocks::ExampleMethods
    # ./spec/support/evm_spec_helper.rb:13:in `<module:EvmSpecHelper>'
    # ./spec/support/evm_spec_helper.rb:12:in `<top (required)>'
    # ./spec/spec_helper.rb:21:in `block in <top (required)>'
    # ./spec/spec_helper.rb:21:in `each'
    # ./spec/spec_helper.rb:21:in `<top (required)>'
    No examples found.

    Finished in 0.00004 seconds (files took 8.12 seconds to load)
    0 examples, 0 failures, 1 error occurred outside of examples

spec/support/evm_spec_helper.rb

@@ -9,6 +9,8 @@
 $log.level = env_level
 Rails.logger.level = env_level
 
+require 'rspec/mocks'
+
 module EvmSpecHelper
   extend RSpec::Mocks::ExampleMethods