man/man2/open_by_handle_at.2: name_to_handle_at(): Document the AT_HANDLE_CONNECTABLE...

man/man2/open_by_handle_at.2: name_to_handle_at(): Document the AT_HANDLE_CONNECTABLE flag

A flag since Linux 6.13 to indicate that the requested file_handle is
intended to be used for open_by_handle_at(2) to obtain an open file
with a known path.

Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Message-ID: <20250331081642.1423812-2-amir73il@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>