Fix PHP version

[xHeaven]

Bumps the PHP version in the benchmark action from 8.4 to 8.5 since we require ^8.5 in composer.json.

[github-actions]

Benchmark Results

Comparison of php-version against main (43ee394a0eedf1479ba50f3209b3371a7d423ddb).

Open to see the benchmark results

_{Generated by phpbench against commit 1cee3e7}