[llvm] [llvm-readobj] Fixes malformed json on JSON printed corefiles (PR #92835)

[Fred Grim via llvm-commits]

feg208 wrote:

> Code looks good, barring a doc issue. Please also update the PR description to match the current change, in particular noting that the LLVM output has been structurally changed to make it work for JSON output too.

@jh7370 I altered the documentation and shortened the commit message along the lines laid out in @ilovepi's comments

https://github.com/llvm/llvm-project/pull/92835