Old approval data isn't cleared if the user changes their level while pending approval

[dwanjuki]

Describe the bug
If a user changes their level while pending approval for another level, details of the pending approval are not cleared from the database.

This can cause an incorrect count to display in the approvals notification badge.

To Reproduce
Steps to reproduce the behavior:

1. In a level group that does not allow multiple selections, set up levels that require admin approval
2. Complete checkout for a level in the group requiring approval.
3. Complete checkout for a different level in the group.
4. Search the usermeta db table for pmpro_approval_ entries associated with your user ID.
5. See that entries exist for the first level checkout

Expected behavior
If a user's level changes while pending approval, the previous level's pending approval data is cleared from the database.

Isolating the problem (mark completed items with an [x]):

• I have deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro plugin is active.
• This bug happens with a default WordPress theme active, or Memberlite.
• I can reproduce this bug consistently using the steps above.

WordPress Environment

WP 6.5.2 PMPro 3.0.3 PMPro Approvals 1.5.1