Clarify the error message to advise to edit the MR to enable squashing

What does this MR do and why?

In gitlab-org/gitlab!93269 (closed) I was confused with the error message "[ ] 0874acc6b15cf34842b73ab957099627efe7b10b: If you are applying suggestions, enable squash in the merge request and re-run the danger-review job.". I was looking everywhere except for within the edit region of the MR. I was used to seeing the squash commit checkbox in the frontend as shown in the screenshot below

This MR clarifies the error message so that the next person no longer wastes time fixing this.

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