[RuntimeAsync] Remove async TODOs where issues are not blocking and tracked in some other way

[VSadov]

Trivial change removing some TODOs.
All these TODOs are for known NYIs that are not blocking and are all tracked in some other way.

Ex:
Multicore JIT: #115097
R2R: #121559
PGO: #121755

[Copilot]

Pull Request Overview

This PR removes TODO comments related to async feature support (Multicore JIT, R2R, PGO, and EnC) that are already tracked in separate issues and are not currently blocking. The changes are purely documentation updates with no code behavior modifications.

• Removes tracked async variant TODOs from ReadyToRunInfo PGO and R2R entry point lookups
• Removes tracked async variant TODO from multicore JIT method recording
• Removes tracked async variant TODO from EnC (Edit and Continue) support

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/coreclr/vm/readytoruninfo.cpp	Removes two TODO comments before early returns for async variants in PGO instrumentation data retrieval and R2R entry point lookups
src/coreclr/vm/multicorejit.cpp	Removes TODO comment in the method preprocessing loop where async variant methods are skipped
src/coreclr/vm/class.cpp	Removes TODO comment before the EnC error log for async methods

[VSadov]

Thanks!