[clang] Revert "[RFC][C++20][Modules] Fix crash when function and lambda insi… (PR #108311)

[Pranav Kant via cfe-commits]

pranavk wrote:

Breaks multiple of our internal workloads and chromium open-source project (https://issues.chromium.org/issues/366045258)

https://github.com/llvm/llvm-project/pull/108311