Do not warn SA1001 (Commas should be spaced correctly) if comma follows a preprocessor directive

Example where I don't think I should need to suppress the diagnostic:
```cs
partial struct Money : IFormattable
#if !NETSTANDARD
#pragma warning disable SA1001 // Commas should be spaced correctly
    , ISpanFormattable
#pragma warning restore SA1001
#endif
```