assert_eq requires PartialEq instead of Eq

[ironcev]

Description

This PR changes the trait constraints on assert_eq and assert_ne from Eq to PartialEq. The Eq requirement was unnecessary strong, and is actually a "leftover" from the original implementation, before we introduced PartialEq.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
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