rem: dev: Remove lock upgrading from the hot path in the QP cache

In QPcache, there were two places that tried to upgrade the lock.  In `clean_stale_header()`, the code would try to upgrade the lock and clean up the header, and in `qpzonode_release()`, the tree lock would be optionally upgraded, so we can clean up the node directly if empty. These
optimizations are not needed and they have no effect on the performance.

Merge branch 'ondrej/no-lock-upgrade-in-check_stale_headers' into 'main'

See merge request isc-projects/bind9!10305