[Clang] [Sema] Fix a crash when a `friend` function is redefined as deleted (#135679)

NB: This only fixes the crash introduced in Clang 19; we still accept
this code even though we shouldn’t:
```c++
struct S {
    friend int f() { return 3; }
    friend int f() = delete;
};
```
I tried figuring out a way to diagnose this redeclaration, but it seems
tricky because I kept running into issues around defaulted comparison
operators. From my testing, however, this fix here would still be
required even once we do start diagnosing this.

Fixes #135506.

0 files changed, 0 insertions, 0 deletions