Throw when act is used in production (#21686)

Upgrades the deprecation warning to a runtime error.

I did it this way instead of removing the export so the type is the same
in both builds. It will get dead code eliminated regardless.

scripts/error-codes/codes.json

@@ -393,5 +393,6 @@
   "402": "The depth must equal at least at zero before reaching the root. This is a bug in React.",
   "403": "Tried to pop a Context at the root of the app. This is a bug in React.",
   "404": "Invalid hook call. Hooks can only be called inside of the body of a function component.",
-  "405": "hydrateRoot(...): Target container is not a DOM element."
+  "405": "hydrateRoot(...): Target container is not a DOM element.",
+  "406": "act(...) is not supported in production builds of React."
 }

scripts/jest/shouldIgnoreConsoleError.js

@@ -35,16 +35,6 @@ module.exports = function shouldIgnoreConsoleError(format, args) {
       // They are noisy too so we'll try to ignore them.
       return true;
     }
-    if (
-      format.indexOf(
-        'act(...) is not supported in production builds of React'
-      ) === 0
-    ) {
-      // We don't yet support act() for prod builds, and warn for it.
-      // But we'd like to use act() ourselves for prod builds.
-      // Let's ignore the warning and #yolo.
-      return true;
-    }
   }
   // Looks legit
   return false;