example-app: remove explicit plugin imports and some unused plugins

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/app/package.json

@@ -19,8 +19,6 @@
     "@backstage/plugin-explore": "^0.3.2",
     "@backstage/plugin-gcp-projects": "^0.2.5",
     "@backstage/plugin-github-actions": "^0.4.2",
-    "@backstage/plugin-github-deployments": "^0.1.2",
-    "@backstage/plugin-gitops-profiles": "^0.2.6",
     "@backstage/plugin-graphiql": "^0.2.9",
     "@backstage/plugin-jenkins": "^0.4.1",
     "@backstage/plugin-kafka": "^0.2.6",
@@ -29,7 +27,6 @@
     "@backstage/plugin-newrelic": "^0.2.6",
     "@backstage/plugin-org": "^0.3.12",
     "@backstage/plugin-pagerduty": "0.3.2",
-    "@backstage/plugin-register-component": "^0.2.12",
     "@backstage/plugin-rollbar": "^0.3.3",
     "@backstage/plugin-scaffolder": "^0.9.0",
     "@backstage/plugin-search": "^0.3.4",