[core] Merge pull request rspec/rspec-core#2731 from rspec/fix-ruby2-…

…keywords-for-other-gems

Prevent rspec-expectations from issuing a warning when combined with rspec-core

---
This commit was imported from rspec/rspec-core@9a96fd4.

rspec-core/lib/rspec/core/example_group.rb

@@ -761,8 +761,9 @@ def method_missing(name, *args)
                 "on an example group (e.g. a `describe` or `context` block)."
         end
 
-        super
+        super(name, *args)
       end
+      ruby2_keywords :method_missing if respond_to?(:ruby2_keywords, true)
     end
     # rubocop:enable Metrics/ClassLength