Remove comment in ZipFile.Create.cs (#86927)

Remove comment in ZipFile.Create.cs (#86927)

* Remove comment in ZipFile.Create.cs

In #85491 the stream-based version of the `DoCreateFromDirectory` override copy-pasted comments from the string-based version
```csharp
// Rely on Path.GetFullPath for validation of sourceDirectoryName and destinationArchive
```
The last clause of that comment is not relevant in the stream-based version (the argument is `Stream destination`) so deleted that clause.

It's possible that the other comment is also misleading as we test the `compressionLevel ` argument just above (unlike in the `String destinationArchive` version
```csharp
            // Checking of compressionLevel is passed down to DeflateStream and the IDeflater implementation
            // as it is a pluggable component that completely encapsulates the meaning of compressionLevel.
```

* Remove compressionLevel validation comment

Co-authored-by: Carlos Sánchez López <1175054+carlossanlop@users.noreply.github.com>
---------

Co-authored-by: Carlos Sánchez López <1175054+carlossanlop@users.noreply.github.com>