comments: fix misuses of "nor"

Signed-off-by: Justin Lebar <jlebar@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -1490,7 +1490,7 @@ sub is_valid_pathname {
 	my $input = shift;
 
 	return undef unless defined $input;
-	# no '.' or '..' as elements of path, i.e. no '.' nor '..'
+	# no '.' or '..' as elements of path, i.e. no '.' or '..'
 	# at the beginning, at the end, and between slashes.
 	# also this catches doubled slashes
 	if ($input =~ m!(^|/)(|\.|\.\.)(/|$)!) {