fuse: remove stray debug line

It wasn't there when the patch was posted for review, but somehow made it
into the pull.

Link: https://lore.kernel.org/all/20240913104703.1673180-1-mszeredi@redhat.com/


Fixes: efad7153 ("fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING_OPEN")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>