[clang-tools-extra] [clang-doc] Add Mustache HTML output to namespace test (PR #169107)

[Paul Kirth via cfe-commits]

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@@ -69,41 +93,61 @@ class AnonClass {};
 // HTML-ANON-INDEX: <h3 id="{{([0-9A-F]{40})}}">anonFunction</h3>
 // HTML-ANON-INDEX: <p>void anonFunction()</p>
 
+// MUSTACHE-ANON-INDEX: <h2> @nonymous_namespace</h2>
+// MUSTACHE-ANON-INDEX:     <h2>Inner Classes</h2>
+// MUSTACHE-ANON-INDEX:         <ul class="class-container">
+// MUSTACHE-ANON-INDEX:             <li id="7CDAAD437F3899C38719F9F23660F4D8B0217B6C" style="max-height: 40px;">
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ilovepi wrote:

```suggestion
// MUSTACHE-ANON-INDEX:             <li id="{{([0-9A-F]{40})}}" style="max-height: 40px;">
```
I assume we want something like this instead, right? I see this in a few more spots.

https://github.com/llvm/llvm-project/pull/169107