[easy] remove leftover reference to disableDefaultPropsExceptForClasses

Noticed that I missed this in some earlier cleanup diff.

Test Plan:
grep for disableDefaultPropsExceptForClasses

Author: kassens

packages/shared/forks/ReactFeatureFlags.test-renderer.native-fb.js

@@ -13,7 +13,6 @@ import typeof * as ExportsType from './ReactFeatureFlags.test-renderer';
 export const alwaysThrottleRetries = false;
 export const disableClientCache = true;
 export const disableCommentsAsDOMContainers = true;
-export const disableDefaultPropsExceptForClasses = true;
 export const disableInputAttributeSyncing = false;
 export const disableLegacyContext = false;
 export const disableLegacyContextForFunctionComponents = false;