[clang] [C++20][Modules] Fix crash when function and lambda inside loaded from different modules (PR #109167)

[Arthur Eubanks via cfe-commits]

aeubanks wrote:

this has also caused the following issue to pop up in our modules build

```
error: variable 'param' cannot be implicitly captured in a lambda with no capture-default specified
```

hopefully the error provides some guidance for where to look, but I can try to get a reduced repro

https://github.com/llvm/llvm-project/pull/109167