[clang] [clang][NFC] Reduce one of JSON dump tests (PR #195026)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

I like this change as well. I don't think having a massive test is helpful. We should have a set of smaller tests that test specific fixes and or features. Maybe I could get behind one large test that is broken into pieces w/ extensive comments in between each section explaining what it is testing in each section but large files are just difficult to maintain.

https://github.com/llvm/llvm-project/pull/195026