Replace path-lock confirmation modal with `GlModal`

Related issue - #344123 (closed)

What does this MR do and why?

Replaces window.confirm in ee/app/assets/javascripts/path_locks.js with GlModal. See &6993 (closed) for more details

Screenshots or screen recordings

before	after

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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