Fix Dismiss button to call expected method

Since Gerrit v3.4.0 the custom Polymer v1 'tap' event is removed and
replaced with the standard 'click' event [1].

[1] 300003: Replace tap by click event | https://gerrit-review.googlesource.com/c/gerrit/+/300003

Change-Id: I700500047780cccc0029d24da55cb837b5380788
Release-Notes: Fixed Dimiss button not persisting until the next day

gr-messageoftheday/gr-messageoftheday-banner_html.js

diff --git a/gr-messageoftheday/gr-messageoftheday-banner_html.js b/gr-messageoftheday/gr-messageoftheday-banner_html.js
index 235633e..5174877 100644
--- a/gr-messageoftheday/gr-messageoftheday-banner_html.js
+++ b/gr-messageoftheday/gr-messageoftheday-banner_html.js
@@ -29,6 +29,6 @@
   <div id="message"></div>
   <gr-button id="dismissMessageBtn"
     link
-    on-tap="_handleDismissMessage">Dismiss</gr-button>
+    on-click="_handleDismissMessage">Dismiss</gr-button>
 </div>
 <gr-rest-api-interface id="restAPI"></gr-rest-api-interface>`;