Use the hashie-forbideen_attributes gem

What does this MR do?

Adds the hashie-forbidden_attributes gem v0.1.1 to the Gemfile. This gem disables mass assignment protection provided by strong_params which is not needed when using Grape because of its own parameter validation, and causes tests to fail when using Ruby 2.1.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

1. To prevent tests from failing with Ruby 2.1
2. To use Grape in the intended way

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #26400 (closed) #23590 (closed)