[clang] [Format] Avoid repeated hash lookups (NFC) (PR #107962)

[Owen Pan via cfe-commits]

================
@@ -86,9 +86,7 @@ void ObjCPropertyAttributeOrderFixer::sortPropertyAttributes(
       Value = Tok->TokenText;
     }
 
-    auto It = SortOrderMap.find(Attribute);
-    if (It == SortOrderMap.end())
-      It = SortOrderMap.insert({Attribute, SortOrderMap.size()}).first;
+    auto It = SortOrderMap.try_emplace(Attribute, SortOrderMap.size()).first;
 
     // Sort the indices based on the priority stored in `SortOrderMap`.
     const auto Ordinal = It->second;
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owenca wrote:

My preference:
```suggestion
    // Sort the indices based on the priority stored in `SortOrderMap`.
    const auto Ordinal =
        SortOrderMap.try_emplace(Attribute, SortOrderMap.size()).first->second;
```
And delete lines 89-91.

https://github.com/llvm/llvm-project/pull/107962