Remove Node 8 from package.json

Author: hsubox76

packages/firestore/package.json

@@ -2,7 +2,7 @@
   "name": "@firebase/firestore",
   "version": "3.1.0",
   "engines": {
-    "node": "^8.13.0 || >=10.10.0"
+    "node": ">=10.10.0"
   },
   "description": "The Cloud Firestore component of the Firebase JS SDK.",
   "author": "Firebase <[email protected]> (https://firebase.google.com/)",