dhcp.cgi: Adjust spacing between an icon and explanatory text

dhcp.cgi: Adjust spacing between an icon and explanatory text

- When dealing with a problem on the forum I noticed that in the Fixed Leases table
   Legend section there was a very large space between the empty checkbox icon and the
   explanatory text. It looks like the &nbsp that I have removed worked on the text
   section 'click to enable' as that was moved but not on the off.gif icon as that stayed
   in its original place leaving a very large space between the icon and the explanatory
   text. Removing the two   commands fixes that.
- Reading up about &nbsp the problem might be related to these tags no longer being
   recommended to use with the newer HTML versions and that indenting or spacing should be
   done via CSS code. Will have a look in future on how to accomplish this via CSS.

Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Bernhard Bitsch <bbitsch@ipfire.org>