MDL-66979 behat: Pad messaging drawer

This works around an issue highlighted by MDL-70411 whereby some of the
messaging links are covered by the scrollbar in Firefox on MacOS.

theme/boost/scss/moodle/debug.scss

@@ -40,6 +40,13 @@ body.behat-site {
             content: none;
         }
     }
+
+    // Workaround for MDL-70411.
+    // Pad the side of the message drawer out slightly to ensure that Firefox scroll bar does not cover controls at the
+    // edge of the screen.
+    [data-region="message-drawer"] {
+        padding-right: 10px;
+    }
 }
 
 .phpinfo table,

theme/boost/style/moodle.css

@@ -18605,6 +18605,9 @@ body.behat-site .custom-control-input {
 body.behat-site .custom-control-label::before, body.behat-site .custom-control-label::after {
   content: none; }
 
+body.behat-site [data-region="message-drawer"] {
+  padding-right: 10px; }
+
 .phpinfo table,
 .phpinfo th,
 .phpinfo h2 {

theme/classic/style/moodle.css

@@ -18787,6 +18787,9 @@ body.behat-site .custom-control-input {
 body.behat-site .custom-control-label::before, body.behat-site .custom-control-label::after {
   content: none; }
 
+body.behat-site [data-region="message-drawer"] {
+  padding-right: 10px; }
+
 .phpinfo table,
 .phpinfo th,
 .phpinfo h2 {