[clang-tools-extra] [clang-doc] remove indentation for preformatted text (PR #166672)

[Erick Velez via cfe-commits]

evelez7 wrote:

We can try just putting them on one line, `<pre><code ...> ... </code></pre>` to reduce the depth.

https://github.com/llvm/llvm-project/pull/166672