[skip ci] Don't generate junit.xml in libmysqlclient for now

We're not uploading it anyway, and it makes the verify generated files
step fail.

Author: iluuu1994

.github/actions/test-libmysqlclient/action.yml

@@ -14,9 +14,7 @@ runs:
         export PDO_MYSQL_TEST_HOST=127.0.0.1
         export PDO_MYSQL_TEST_USER=root
         export PDO_MYSQL_TEST_PASS=root
-        export TEST_PHP_JUNIT=junit.xml
         export REPORT_EXIT_STATUS=no
-        rm -rf junit.xml | true
         sapi/cli/php run-tests.php -P -q \
           -g FAIL,XFAIL,BORK,WARN,LEAK,XLEAK,SKIP \
           --offline --show-diff --show-slow 1000 --set-timeout 120 \