fix: remove alias rigid before calling relate

[cordx56]

This PR fixes #158773.
This fix resolves regression from at least nightly 1.96.0, as I checked.

Cause of issue

In the current code, relate(a, b) is called on the type SameTypeModuloInfer, which is outside of the trait resolver.
So the rigid should be removed.

I inserted ty::set_aliases_to_non_rigid before calling relate method and now it works correctly.

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[cordx56]

Hi, @adwinwhite. I found the issue is easily resolved and fixed in this PR.

If you already working on this problem, sorry for taking it without your confirm.
And if you find any problems, I would appreciate any comments.