Upgrade @octokit/rest

Signed-off-by: Erik Engervall <erik.engervall@gmail.com>

plugins/git-release-manager/package.json

@@ -27,7 +27,7 @@
     "@material-ui/core": "^4.11.0",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",
-    "@octokit/rest": "^18.0.12",
+    "@octokit/rest": "^18.5.3",
     "luxon": "^1.26.0",
     "qs": "^6.10.1",
     "react-dom": "^16.13.1",