luci-mod-network: i18n fix

luci-mod-network: i18n fix

Follow-up fix to fb4cf432d2232a0ba2ccd3a8ff81a3679c8d054d

Resolves sync errors:

standard input:682: warning: Empty msgid.  It is reserved by GNU gettext:
                             gettext("") returns the header entry with
                             meta information, not the empty string.
standard input:733: warning: Empty msgid.  It is reserved by GNU gettext:
                             gettext("") returns the header entry with
                             meta information, not the empty string.
standard input:761: warning: Empty msgid.  It is reserved by GNU gettext:
                             gettext("") returns the header entry with
                             meta information, not the empty string.
standard input:818: warning: Empty msgid.  It is reserved by GNU gettext:
                             gettext("") returns the header entry with
                             meta information, not the empty string.

Signed-off-by: Paul Donald <newtwen+github@gmail.com>