chore: don't automerge npm and yarn

renovate.json

@@ -24,6 +24,10 @@
     "Sourcegraph"
   ],
   "packageRules": [
+    {
+      "packageNames": ["npm", "yarn"],
+      "automerge": false
+    },
     {
       "depTypeList": ["dependencies"],
       "semanticCommitType": "build"