[clang] [docs] alias attribute doc (PR #193652)

[Aaron Ballman via cfe-commits]

================
@@ -9983,3 +9983,37 @@ different languages to coexist on the same call stack while each interpreting
 exceptions according to their own rules.
   }];
 }
+
+def AliasDocs : Documentation {
+  let Category = DocCatFunction;
----------------
AaronBallman wrote:

```suggestion
  let Category = DocCatDecl;
```
The attribute applies to functions and global variables, so it's more of a declaration attribute than a function one.

https://github.com/llvm/llvm-project/pull/193652