Reword merge details in merge request merge widget

The following discussion from !71721 (merged) should be addressed:

• @pedroms started a discussion: (+3 comments)

  @aqualls 💡 thought (text,non-blocking): today the “merge details” (what will happen when the MR is merged) are worded differently from each other. Some use will be, others don't. Some have the noun in the beginning, others have the verb.

  1 merge commit will be added to master
  Source branch will be deleted
  Source branch will not be deleted
  Closes issue #123

  This is the structure I had originally proposed, starting with the noun and using will be.

  Can edit	Cannot edit

  However, I'm unsure what's preferable in this situation: to start with the noun or with the verb. Alternatively, it could read:

  Adds 1 merge commit to master
  Deletes the source branch
  Does not delete the source branch
  Closes issue #123

  I'm adding this as a comment here, but depending on your feedback, it might make sense to move this to a dedicated issue.