[clang-tools-extra] [clang-doc] refactor JSON for better Mustache compatibility (PR #149588)

[Erick Velez via cfe-commits]

evelez7 wrote:

### Merge activity

* **Jul 23, 7:51 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/149588).


https://github.com/llvm/llvm-project/pull/149588