Remove disableIEWorkarounds (#31756)

Based off https://github.com/facebook/react/pull/31755

This is landed everywhere.

scripts/jest/setupTests.www.js

@@ -15,7 +15,6 @@ jest.mock('shared/ReactFeatureFlags', () => {
   // These are hardcoded to true for the next release,
   // but still run the tests against both variants until
   // we remove the flag.
-  actual.disableIEWorkarounds = __VARIANT__;
   actual.disableClientCache = __VARIANT__;
 
   return actual;