Fix several RxJava2Adapter Refaster templates

[Stephan202]

Suggested commit message:

Fix several `RxJava2Adapter` Refaster templates (#205)

This reverts some changes from d2bbee3ed9953598d3e75ff5bd381a2616b8693d
and instead drops some invalid `Flowable#compose` and `Flux#transform`
rewrite rules.

Commit referenced is d2bbee3.

[rickie]

Good catch, the subtle change I missed was the return type...

I saw in Platform that the Refaster template for (e.g.) RxJava2Adapter.flowableToFlux(flowable), wasn't changed, so I added them in EPS.
After running the self-check I saw that the IdentityConversion check is supposed to rewrite those. However, this solution is more accurate and better.

[Stephan202]

I saw in Platform that the Refaster template for (e.g.) RxJava2Adapter.flowableToFlux(flowable), wasn't changed, so I added them in EPS.

That's exactly how I started out on this journey as well 😅. But then I noticed that the downstream patch script didn't rewrite those expressions either, so at that the point the question became "why does IdentityConversion trigger in one context, but not the other?". Now we know :)

[ibabiankou]

LGTM, though RxJava/Reactor is not my strongest skill 😅