gitweb: [commit view] Do not suppress commitdiff link in root commit

There's no reason for that, the commitdiff view is meaningful for the
root commit as well and we link to it everywhere else.

Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -2957,7 +2957,7 @@ sub git_commit {
 			        "blame");
 	}
 	git_header_html(undef, $expires);
-	git_print_page_nav('commit', defined $co{'parent'} ? '' : 'commitdiff',
+	git_print_page_nav('commit', '',
 	                   $hash, $co{'tree'}, $hash,
 	                   join (' | ', @views_nav));