fix(notifications) drop no longer used css file (#13100)

css/_notifications.scss

@@ -1,23 +0,0 @@
-.notification-appear, .notification-enter {
-    opacity: 0;
-    position: relative;
-    left: -200px;
-    transition: all .2s !important; // !important needed to overwrite atlaskit default style
-
-    &-active {
-        opacity: 1;
-        left: 0;
-    }
-}
-
-.notification-exit {
-    opacity: 1;
-    position: relative;
-    left: 0;
-    transition: all .2s !important; // !important needed to overwrite atlaskit default style
-
-    &-active {
-        opacity: 0;
-        left: -200px;
-    }
-}

css/main.scss

@@ -89,6 +89,5 @@ $flagsImagePath: "../images/";
 @import 'reactions-menu';
 @import 'plan-limit';
 @import 'polls';
-@import 'notifications';
 
 /* Modules END */