Bump request-promise from 4.2.5 to 4.2.6 in /frontend

Bumps [request-promise](https://github.com/request/request-promise) from 4.2.5 to 4.2.6.
- [Release notes](https://github.com/request/request-promise/releases)
- [Commits](request/request-promise@v4.2.5...v4.2.6)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

frontend/package-lock.json

@@ -10,7 +10,7 @@
     "react-dom": "^16.13.1",
     "react-router-dom": "^5.2.0",
     "react-scripts": "^3.4.0",
-    "request-promise": "^4.2.5"
+    "request-promise": "^4.2.6"
   },
   "scripts": {
     "start": "react-scripts start",