[clang-tools-extra] [clang-doc] refactor JSONGenerator array usage (PR #145595)

[Paul Kirth via cfe-commits]

https://github.com/ilovepi approved this pull request.

LGTM. Glad to see so much code getting deleted! Overall great cleanups. Left a couple small comments inline.

https://github.com/llvm/llvm-project/pull/145595