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

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-HTTPPROXYMIDDLEWARE-9691387
- https://snyk.io/vuln/SNYK-JS-HTTPPROXYMIDDLEWARE-9691389

Author: snyk-io[bot]

plugins/airbrake-backend/package.json

@@ -24,11 +24,11 @@
   "dependencies": {
     "@backstage/backend-common": "workspace:^",
     "@backstage/backend-plugin-api": "workspace:^",
-    "@backstage/config": "workspace:^",
+    "@backstage/config": "0.1.1",
     "@types/express": "*",
     "express": "^4.17.1",
     "express-promise-router": "^4.1.0",
-    "http-proxy-middleware": "^2.0.0",
+    "http-proxy-middleware": "^2.0.9",
     "winston": "^3.2.1",
     "yn": "^4.0.0"
   },