[clang] [clang] reject to capture variable in `RequiresExprBodyDecl` (PR #78598)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

> @cor3ntin @shafik Hi, I want to take charge of this issue and submit a PR for the fix.

I would open a new PR and reference this one in the summary for completeness. It looks like this one is not going to picked up by the author and so if you can take it over and finish it that would be very much appreciated. 

There are a lot of issues that crash similarly and so we likely have plenty of tests to try against a fix :-)

https://github.com/llvm/llvm-project/pull/78598