fix: plugins/events-backend/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-TAR-15032660
- https://snyk.io/vuln/SNYK-JS-TAR-15127355
- https://snyk.io/vuln/SNYK-JS-ESLINT-15102420

Author: snyk-bot

plugins/events-backend/package.json

@@ -36,9 +36,9 @@
   },
   "dependencies": {
     "@backstage/backend-common": "workspace:^",
-    "@backstage/backend-plugin-api": "workspace:^",
-    "@backstage/config": "workspace:^",
-    "@backstage/plugin-events-node": "workspace:^",
+    "@backstage/backend-plugin-api": "0.6.19",
+    "@backstage/config": "0.1.1",
+    "@backstage/plugin-events-node": "0.2.9",
     "@types/express": "^4.17.6",
     "express": "^4.17.1",
     "express-promise-router": "^4.1.0",