Previously, this relied on PHP itself to release locks during the resource destructor phase during process exit, but sometimes it doesn't for god knows what reason. This change makes the lock file get explicitly released before the process dies.
fixes a phpstan level 7 error
phpstan doesn't make any assumptions about local static variable types because analysing them would require too much work, apparently.
we really need the level 8 checks on new code now, and waiting until old code is clean is not going to benefit us much because the issues that are there already exist.
