FE: Update deprecation banners to show scan result policies being deprecated

Why are we doing this work

To better convey that type: scan_result_policy policies are being deprecated, we should update the alert.

Relevant links

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

• update deprecation/removal banner
  • Fix name in banner: Merge result policy → Merge request approval policy
  • Error in the text there for what we are changing in newly_detected
  • Update text to also include scan result policy text

Verification steps