man: Make "Filtering rules" section more prominent

[DanielG]

The .TP made the heading indented quite deeply whereas I think it should be at the same level as the "Interface configuration" section.

Before:

   Interface configuration
       An interface is configured by a line with the following format:

              interface name [parameter...]
[...]
       accept-bad-signatures {true|false}
              Accept  packets  with  no  signature  or an incorrect signature.
              This only has an effect if a key was configured on an interface.
              The default is false.

          Filtering rules
              A  filtering rule is defined by a single line with the following
              format:

              filter selector...  action

After:

       accept-bad-signatures {true|false}
              Accept  packets  with  no  signature  or an incorrect signature.
              This only has an effect if a key was configured on an interface.
              The default is false.

   Filtering rules
       A filtering rule is defined by a single line with the following format:

              filter selector...  action

[jech]

Merged, thanks.