Add feature category to Mutations::Ci::JobTokenScope::RemoveProject spec

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR adds a feature cateogry tag to a GraphQL mutation spec that doesn't currently have one. I'm currently working on it, and it's definitely part of the Category:Continuous Integration work.

How to set up and validate locally

The standard unlabeled-spec warnings go away on my feature change here:

$ git checkout master
$ bundle exec rspec spec/graphql/mutations/ci/job_token_scope/remove_project_spec.rb
Run options: include {:focus=>true}

All examples were filtered out; ignoring {:focus=>true}

Test environment set up in 4.421384 seconds
Missing metadata feature_category: ./spec/graphql/mutations/ci/job_token_scope/remove_project_spec.rb:28 See https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#feature-category-metadata
.Missing metadata feature_category: ./spec/graphql/mutations/ci/job_token_scope/remove_project_spec.rb:37 See https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#feature-category-metadata
.Missing metadata feature_category: ./spec/graphql/mutations/ci/job_token_scope/remove_project_spec.rb:48 See https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#feature-category-metadata
.Missing metadata feature_category: ./spec/graphql/mutations/ci/job_token_scope/remove_project_spec.rb:57 See https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#feature-category-metadata
.

Finished in 7.04 seconds (files took 8.61 seconds to load)
4 examples, 0 failures

$ git fetch origin add-feature-category-to-remove-token-scope-link-mutation
$ git checkout origin/add-feature-category-to-remove-token-scope-link-mutation
$ bundle exec rspec spec/graphql/mutations/ci/job_token_scope/remove_project_spec.rb
Run options: include {:focus=>true}

All examples were filtered out; ignoring {:focus=>true}

Test environment set up in 4.420646 seconds
....

Finished in 6.97 seconds (files took 8.4 seconds to load)
4 examples, 0 failures

MR acceptance checklist

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