btrfs: update comment for try_release_extent_state()

btrfs: update comment for try_release_extent_state()

Drop reference to pages from the comment since the function is fully folio
aware and works regardless of how many pages are in the folio. Also while
at it, capitalize the first word and make it more explicit that
release_folio is a callback from struct address_space_operations.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>