Keep <style> blocks when scrubbing dashboard emails

Dashboard email is scrubbed after its CSS is imported into <style> blocks,
but HTML::Scrubber drops <style> by default, so the CSS was stripped whenever
it was not inlined into element style="" attributes (the default, and also
when CSS::Inliner skips large content). Enable the scrubber's style flag so
the CSS survives.

Author: sunnavy

lib/RT/Dashboard/Mailer.pm

@@ -1015,6 +1015,8 @@ sub _RunHeadlessBrowser {
                 },
             );
 
+            # Allow style as it's off by default
+            $scrubber->style(1);
         }
         return $scrubber;
     }