Use Observable from @backstage/core

Signed-off-by: Marcus Eide <eide@spotify.com>

plugins/shortcuts/package.json

@@ -41,7 +41,6 @@
     "@testing-library/user-event": "^12.0.7",
     "@types/jest": "^26.0.7",
     "@types/node": "^14.14.32",
-    "@types/zen-observable": "^0.8.2",
     "cross-fetch": "^3.0.6",
     "msw": "^0.21.2"
   },

plugins/shortcuts/src/api/ShortcutApi.ts

@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-import Observable from 'zen-observable';
-import { createApiRef } from '@backstage/core';
+import { createApiRef, Observable } from '@backstage/core';
 import { Shortcut } from '../types';
 
 export const shortcutsApiRef = createApiRef<ShortcutApi>({