[generator] Fix invalid code generated for EventArgs classes with parameter arrays.

[jpobst]

Fixes: #817

If we are creating an EventArgs class for a method that has a parameter array like this:

public interface SomeListener {
    void onSomeNotification (Object... args);
}

We are generating the following invalid C# code:

public partial class SomeEventArgs : global::System.EventArgs {
    params global::Java.Lang.Object[] args;

    public params global::Java.Lang.Object[] Args {
        get { return args; }
    }
}

This commit removes the extraneous params output.