[clang] [Clang] [CodeGen] Perform derived-to-base conversion on explicit object parameter in lambda (PR #89828)

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Sirraide wrote:

> Should I just run make_cxx_dr_status again then and commit the result?

I ended up figuring it out after talking to @Endilll about it. 

Also, the only CI failure earlier was something unrelated (CoverageMapping/mcdc-system-headers.cpp).

https://github.com/llvm/llvm-project/pull/89828