Slight improvement to retry.

Before, if server didn't suggest a retry interval, we'd do it immediately!

Author: coke

xt/rakudoc-l.rakutest

@@ -118,7 +118,7 @@ sub is-valid-link($links) {
                     when X::Cro::HTTP::Error {
                         if .response.status == 429 {
                             diag "HTTP 429 $link";
-                            my $retry-after = .response.header('retry-after');
+                            my $retry-after = .response.header('retry-after') // 5;
                             sleep $retry-after;
                             redo;
                         } else {