[llvm] [coro][pgo] Remove redundant coroutine test files (PR #89620)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

This was intentional, see the comment that introduced them (https://github.com/llvm/llvm-project/pull/71262#pullrequestreview-1723261241)

An advantage is that the tests cover 2 concerns, really: coro lowering, and PGO instrumentation. They can potentially diverge if needed. 

Other than needing to duplicate a fix in both places, is there any other shortcoming of the double presence?

+david-xl who suggested the change originally.

https://github.com/llvm/llvm-project/pull/89620