Disable prop-types check in ESLint config

Prop-types checking has been replaced by static checking done by
TypeScript.

.eslintrc

@@ -9,6 +9,9 @@
 
     // https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html#eslint
     "react/jsx-uses-react": "off",
-    "react/react-in-jsx-scope": "off"
+    "react/react-in-jsx-scope": "off",
+
+    // Replaced by TypeScript's static checking.
+    "react/prop-types": "off"
   }
 }