Replace $.ajax in project.js

What does this MR do?

Replace $.ajax in project.js.

There are multiple specs that cover this change:

• features/steps/project/network_graph.rb
• features/steps/project/source/browse_files.rb
• spec/features/commits_spec.rb
• features/merge_request/user_sees_merge_widget_spec.rb
• spec/features/projects/user_browses_files_spec.rb

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

jQuery ajax => axios

Why was this MR needed?

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
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/42397