gitweb: Use capturing parentheses only when you intend to capture

Non-capturing groups are useful because they have better runtime
performance and do not copy strings to the magic global capture
variables.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -828,7 +828,7 @@ if (!defined $action) {
 if (!defined($actions{$action})) {
 	die_error(400, "Unknown action");
 }
-if ($action !~ m/^(opml|project_list|project_index)$/ &&
+if ($action !~ m/^(?:opml|project_list|project_index)$/ &&
     !$project) {
 	die_error(400, "Project needed");
 }