fix: change default generics type parameter of CustomMatchers

[nozomuikuta]

Description

Resolves #7731

I just changed default generics type parameter, from unknown to any, as described in the issue.

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[nozomuikuta]

Hmm, I'm not sure why some CI fails...

[sheremet-va]

I think we should instead recommend using Matchers interface, and deprecate this one. Matchers interface is applied to expect.extend and expect.to* too.