Fix merge commit 5ea5291d: No test file or result files should be executable

In commit 5ea5291d @sanja-byelkin for unknown reason switched the file mode
for 3 Galera tzinfo related test files from 644 -> 755. This exists only
from branch 10.6 onward:

    $ git checkout 10.5
    $ find mysql-test -executable -name *.test -or -executable -name *.result
    (no results)
    $ git checkout 10.6
    $ find mysql-test -executable -name *.test -or -executable -name *.result
    mysql-test/suite/galera/t/mysql_tzmysql-test/suite/galera/t/mysql_tzinfo_to_sql.test
    mysql-test/suite/galera/t/mariadb_tzinfo_to_sql.test
    mysql-test/suite/galera/r/mariadb_tzinfo_to_sql.resultinfo_to_sql.test

mysql-test/suite/galera/t/mariadb_tzinfo_to_sql.test
mysql-test/suite/galera/r/mariadb_tzinfo_to_sql.result

No test file nor test result file should be executable, so run chmod -x
on them.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.