Revisit visionOS Hermes in our version of RNTester

[amgleitman]

While working on #2530, we found some weirdness with getting RNTester to compile with visionOS Hermes in our CIs. Given that our main focus is macOS (a separate repo exists for RN in visionOS) and that RNTester is an anomaly in that we bundle multiple platforms under the same Xcode project (as opposed to the usual strategy of one Xcode project for each platform), this may not be a showstopper, but it would still be nice to get it working anyway.