swapon: improve a translator hint, and remove a pointless one

swapon: improve a translator hint, and remove a pointless one

The reference to "each entry below" made no sense, as that second
translator hint is not before a gettextized message and therefore
did not make it into the POT file.  Gettextizing that message is
not useful as 1) there is nothing to translate, and 2) allowing
the translators to fiddle with the tabs is too complicated, and
3) the --summary output is deprecated anyway.

Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>