Remove deprecated ActionDispatch::ParamsParser

What does this MR do?

Fixes deprecation: DEPRECATION WARNING: ActionDispatch::ParamsParser is deprecated and will be removed in Rails 5.1. Configure the parameter parsing in ActionDispatch::Request.parameter_parsers. (called from block (2 levels) in <top (required)> at /builds/gitlab-org/gitlab-ce/spec/lib/gitlab/middleware/read_only_spec.rb:15)

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer