Make restoring backup database table warning more explicit

What does this MR do?

Makes the restoring backup warning more explicit: from

Before restoring the database we recommend removing all existing
tables to avoid future upgrade problems. Be aware that if you have
custom tables in the GitLab database these tables and all data will be
removed.

to

Before restoring the database, we will remove all existing
tables to avoid future upgrade problems. Be aware that if you have
custom tables in the GitLab database these tables and all data will be
removed.

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

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

What are the relevant issue numbers?

Closes #39903 (closed)