Resolve -Wdocumentation warning in ClangTidyDiagnosticConsumer (NFC)

Change to comments only; NFC.

```
ClangTidyDiagnosticConsumer.h:245:6: warning: '\param' command used in a
comment that is not attached to a function declaration [-Wdocumentation]
```

See this build for an example:
https://lab.llvm.org/buildbot/#/builders/109/builds/27293/steps/5/logs/warnings__702_