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

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-DIFF-14917201
- https://snyk.io/vuln/SNYK-JS-BACKSTAGEBACKENDPLUGINAPI-15054291
- https://snyk.io/vuln/SNYK-JS-LODASH-15053838
- https://snyk.io/vuln/SNYK-JS-LODASHES-15053836

Author: snyk-io[bot]

plugins/events-backend-module-gerrit/package.json

@@ -35,8 +35,8 @@
     "postpack": "backstage-cli package postpack"
   },
   "dependencies": {
-    "@backstage/backend-plugin-api": "workspace:^",
-    "@backstage/plugin-events-node": "workspace:^",
+    "@backstage/backend-plugin-api": "1.6.1",
+    "@backstage/plugin-events-node": "0.4.0",
     "winston": "^3.2.1"
   },
   "devDependencies": {