Resolve "Add merge_request_diff_head_sha to CreateNote input parameters"

What does this MR do and why?

Allow the user to use the /merge quick action in graphql create note

To Test

Create a merge request that can be merged.

• On master try the request
• It should fail as the parameter is unknown
• Switch to this branch
• Run the Request
• It should merge the branch

Graphql Query

mutation MergeCommand {
    createNote(input: { noteableId: "gid://gitlab/MergeRequest/3734", body: "/merge", #mergeRequestDiffHeadSha: "5bb0c8abd043446fc72f987198c325e08c2599f4"}) {
      errors
    }
  }

Related to #354091 (closed)