Fix super set for VSTHRD103

[Tobbeman]

Fixes bug raised here: #1422

The method of HasSupersetOfParameterTypes confused me as I think the check was inverted?
I took the liberty to change that as well, but let me know if I understand it wrong.

Any and all feedback is appreciated

[Tobbeman]

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[Tobbeman]

On further thinking; would it not be better to be strict here, ensuring the method is a strict match or strict match + cancellationToken?

The current code will match, regardless of my change or not

void Bar(int i1) {}
Task BarAsync(int i1, int i2, int i3, int i4) => Task.CompletedTask

Only matching same arguments + optional cancellation token:

void Bar(int i1) {}
Task BarAsync(int i1, int i2, int i3, int i4) => Task.CompletedTask
Task BarAsync(int i1) => Task.CompletedTask // Match
Task BarAsync(int i1, CancellationToken t) => Task.CompletedTask // Match