ci: enforce request review on the final state

In apache#5940 (comment),
during solving the merge conflict,
a bug which is fixed in apache#6204 is
reintroduced.
The test is also changed so it can't catch up the regression.

That PR is approved before merging the master. Luckily, I am cautious
enough to start another turn of review.

We should not rely on the lucky or someone else's caution.
To prevent that from happening again, here we enforce the approval
should be applied with the final state.

Signed-off-by: spacewander <[email protected]>

.asf.yaml

@@ -45,6 +45,7 @@ github:
     protected_branches:
       master:
         required_pull_request_reviews:
+          dismiss_stale_reviews: true
           require_code_owner_reviews: true
           required_approving_review_count: 2
       release/2.12: