Comment in try-catch exception parameter not highlighting

## Details

VS Code version: 1.24.0
C# Extension version: 1.15.2

## Steps to reproduce
```
try { /* Stuff */ }
catch ( ExceptionType /* This comment isn't highlighted as a comment */ ) { /* stuff */ }
```

This is part of example code from the ASP.Net Core tutorials https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/crud?view=aspnetcore-2.1

## Expected behavior
The comment inside the parentheses should be highlighted as a comment.

## Actual behavior
The comment inside the parentheses is highlighted as a variable name, as if it were an ExceptionType.