fix packaging of lang/clisp after removal of USE_GROFF

Hi,

without groff, the manpages for clisp(1) and clisp-link(1) aren't
rendered to PostScript output any longer, so just remove the .ps
entries from the plist.

ok?

Index: pkg/PLIST
===================================================================
RCS file: /cvs/ports/lang/clisp/pkg/PLIST,v
retrieving revision 1.16
diff -u -p -r1.16 PLIST
--- pkg/PLIST 6 Oct 2015 11:37:06 -0000 1.16
+++ pkg/PLIST 2 Jun 2017 21:41:04 -0000
@@ -66,11 +66,9 @@ share/doc/clisp/README.es
share/doc/clisp/SUMMARY
share/doc/clisp/clisp-link.1
share/doc/clisp/clisp-link.html
-share/doc/clisp/clisp-link.ps
share/doc/clisp/clisp.1
share/doc/clisp/clisp.html
share/doc/clisp/clisp.png
-share/doc/clisp/clisp.ps
share/doc/clisp/impnotes.css
share/doc/clisp/impnotes.html
share/doc/clisp/lisp.vim