[Coroutines][Docs] Remove frame packing as a TODO

[atmnpatel]

Summary

This has already been done by @rjmccall in D76526 (49e5a97ec363), and
9514c048d89e. We should remove this from the docs.

[rjmccall]

I'm not sure how overlap-aware our packing is, but yeah, I'm fine with removing this.

llvm/docs/Coroutines.rst

 
 CoroCleanup
 -----------
 This pass runs late to lower all coroutine related intrinsics not replaced by
 earlier passes.
 
 Areas Requiring Attention
 =========================
-#. A coroutine frame is bigger than it could be. Adding stack packing and stack 
-   coloring like optimization on the coroutine frame will result in tighter
-   coroutine frames.
-
 #. Take advantage of the lifetime intrinsics for the data that goes into the
    coroutine frame. Leave lifetime intrinsics as is for the data that stays in
    allocas.
 
 #. The CoroElide optimization pass relies on coroutine ramp function to be
    inlined. It would be beneficial to split the ramp function further to 
    increase the chance that it will get inlined into its caller.