Re-enable two previously-skipped LayoutAnimation stress tests (#56883)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/56883

Two parameterized `LayoutAnimationTest` stress tests have been marked `GTEST_SKIP()` since early 2024, when the default Yoga `position` was switched from `absolute` to `relative`. The skip was added as a temporary measure while the test expectations diverged from the new default.

The underlying issue appears to have been resolved by subsequent work on the layout differ / mounting pipeline.

Changelog: [Internal]

Differential Revision: D105661336

fbshipit-source-id: 7b0a89c6e7b24b903a6a792d8e82b3aee8d94bd6