Devel::PPPort: Fix broken pod link

ppport.h is pod, but the link to it, removed by this commit, is broken,
resulting in a 404 "Raptor not found" from

https://perldoc.perl.org/Devel::PPPort#SEE-ALSO

This commit changes the mention of the file from a link to a F<>.

Author: khwilliamson

dist/Devel-PPPort/PPPort_pm.PL

@@ -747,7 +747,7 @@ modify it under the same terms as Perl itself.
 
 =head1 SEE ALSO
 
-See L<h2xs>, L<ppport.h>.
+See L<h2xs>, F<ppport.h>.
 
 =cut
 

t/porting/known_pod_issues.dat

@@ -389,7 +389,6 @@ YAML
 YAML::Syck
 YAML::Tiny
 dist/data-dumper/dumper.pm	? Should you be using L<...> instead of	1
-dist/devel-ppport/ppport.pm	Apparent broken link	1
 dist/env/lib/env.pm	? Should you be using F<...> or maybe L<...> instead of	1
 dist/math-complex/lib/math/complex.pm	Verbatim line length including indents exceeds 78 by	3
 dist/math-complex/lib/math/trig.pm	Verbatim line length including indents exceeds 78 by	4