Remove faulty Pair.invert tests
Remove faulty Pair.invert tests

The tests index return value with `[0]` failing to check what type
the return value is. Due to this, they failed to detect a bug where
.invert was returning a Pair instead of a Seq in some cases.

That bug is now fixed[^1] and I'm removing these tests entirely,
because new, more comprehensive tests added[^2] earlier today cover
the tested cases already.

[1] https://github.com/rakudo/rakudo/commit/7ea0f66189
[2] https://github.com/perl6/roast/commit/f4828aaf64

bitrauser/roast,bitrauser/roast,dogbert17/roast,dogbert17/roast,perl6/roast