Remove the code that "locked" the .fs-verity keyring at a certain point
in the boot. It probably was thought that this achieved some useful
security property, which is a bit questionable. Regardless, Android no
longer uses fsverity builtin signatures. The only code that is still
being kept around is enough to access existing files on old kernels, and
for this "locking" the keyring is definitely not essential.
Bug: 290064770
Test: presubmit and booting Cuttlefish
Change-Id: Ide5729aeac5772658b2a3f0abe835988b8842b02
79a67391bd