chore(ci): labeler v5.0.0 is inconsistent (#3978)

Despite the fact that the labeler v5.0.0 demands a different syntax
for the configuration file, it has inconsistent behavior:

actions/labeler#712 (comment)

So, return to the most recent version that works as expected.

.github/workflows/labeler.yml

@@ -12,4 +12,4 @@ jobs:
       pull-requests: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/labeler@8558fd74291d67161a8a78ce36a881fa63b766a9 # v5.0.0
+      - uses: actions/labeler@ac9175f8a1f3625fd0d4fb234536d26811351594 # v4.3.0