Fix false positive in `PartialEq` check in `unconditional_recursion` lint
Fixes https://github.com/rust-lang/rust-clippy/issues/12133.
We needed to check for the type of the previous element <del>in case it's a field</del>.
EDIT: After some extra thoughts, no need to check if it's a field, just if it's the same type as `Self`.
r? `@llogiq`
changelog: Fix false positive in `PartialEq` check in `unconditional_recursion` lint