fix(mount): don't release file handles from FUSE Forget (#9529)

fix(mount): don't release file handles from Forget

Forget(nodeid, nlookup) only decrements the kernel inode lookup count.
File handle lifecycle belongs to FUSE Open/Release. Driving the FH
refcount from Forget coupled two unrelated counters and could tear down
a still-live handle if Forget ever raced ahead of Release.

Drop the ReleaseByInode call (and the now-unused method).