feat(deps): update atlaskit/dropdown-menu to 6.1.12

This is a pre-requisite to updating atlaskit/tabs to 8.0.8.
Without updating, clicking a dropdown menu within a tab
component within a modal, such as the language selector in
the settings dialog, will lock the browser.

css/_atlaskit_overrides.scss

         background-color: #172B4D;
     }
 }
+
+.modal-dialog-form {
+    /**
+     * Update the dropdown trigger wrapper to make sure it looks click-able.
+     */
+    .gwEjuO {
+        cursor: pointer;
+    }
+
+    /**
+     * Override Atlaskit dropdown styling when in a modal because the dropdown
+     * backgrounds clash with the modal backgrounds.
+     */
+    .gBLqhw[data-role=droplistContent] {
+        border: 1px solid #455166;
+    }
+}

css/modals/_dialog.scss

     &-error {
         margin-bottom: 8px;
     }
-
-    /**
-     * Override Atlaskit dropdown styling when in a modal because the dropdown
-     * backgrounds clash with the modal backgrounds.
-     */
-    .htclLc[data-role=droplistContent] {
-        border: 1px solid #455166;
-    }
 }
 .modal-dialog-footer {
     font-size: $modalButtonFontSize;

package.json

     "@atlaskit/avatar": "14.0.10",
     "@atlaskit/button": "9.0.8",
     "@atlaskit/checkbox": "4.0.6",
-    "@atlaskit/dropdown-menu": "3.10.2",
+    "@atlaskit/dropdown-menu": "6.1.12",
     "@atlaskit/field-text": "7.0.10",
     "@atlaskit/field-text-area": "4.0.9",
     "@atlaskit/flag": "6.1.0",