[clang] The error message for `-gen-reproducer=error` should not request a bug report

We have observed the following sequence output when an error occurs with `-gen-reproducer=error`:

```
clang++: error: failing because '-gen-reproducer' is used
Fuchsia clang version 22.0.0git (https://llvm.googlesource.com/llvm-project 46e9d6325a825b516826d0c56b6231abfaac16ab)
Target: aarch64-unknown-fuchsia
Thread model: posix
InstalledDir: ../../prebuilt/third_party/clang/custom/bin
Build config: +assertions
clang++: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: clang-crashreports/vnode-cdfcdd.cpp
clang++: note: diagnostic msg: clang-crashreports/vnode-cdfcdd.sh
clang++: note: diagnostic msg:

********************
```

The mention of a bug report is confusing; it implies that there is a bug in the compiler, and there isn't in this case. This caused a downstream bug to be misfiled by an oncall-er who thought they were looking at a clang crash. Ideally, none of the produced text would imply that there's anything wrong with clang in the case that clang did not itself actually crash.