Sync Bug 1399245: Fix mozilla/normandy#1036: Remove OSX-specific close button CSS for Heartbeat bar. r=Gijs

Due to changes in browser styles for Photon, the fix is no longer necessary, and
in fact makes the close button look wrong. Without the fix, the close button
looks and behaves the same as the tab bar close buttons.

MozReview-Commit-ID: 89tCvQAq1OR

--HG--
extra : rebase_source : 772e21d5ff1b41c31efb0c0461aa60e08a0b4372

browser/extensions/shield-recipe-client/skin/osx/Heartbeat.css

@@ -9,16 +9,3 @@ notification.heartbeat {
   border-bottom: 1px solid #C1C1C1 !important;
   height: 40px;
 }
-
-/* In themes/osx/global/notification.css the close icon is inverted because notifications
-   on OSX are usually dark. Heartbeat is light, so override that behaviour. */
-
-notification.heartbeat[type="info"] .close-icon:not(:hover) {
-  -moz-image-region: rect(0, 16px, 16px, 0) !important;
-}
-
-@media (min-resolution: 2dppx) {
-  notification.heartbeat[type="info"] .close-icon:not(:hover) {
-    -moz-image-region: rect(0, 32px, 32px, 0) !important;
-  }
-}