fix: tests with migrations_lock

[michalsn]

Description
This PR fixes tests migrations by ensuring the migrations_lock table is always removed.

No changelog entry, as this change is relevant only for tests.

Fixes #9832

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[neznaika0]

Does this mean that *_lock is not needed all the time? After each lock, the table must be deleted.

[michalsn]

@neznaika0 If we use migrations_lock, then the table should exist at all times. Deleting it defeats the purpose of having the locking mechanism in the first place. There is also no safe moment to remove it automatically - once one process finishes running migrations, another process may already be in progress and still need to check the lock status.

In tests, however, we drop this table, as it is only needed for a few specific test cases.

[michalsn]

Thank you for the reviews!