[AsmParser] Avoid repeated map lookups (NFC) (#123015)

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 81d048b..be6166f 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -941,8 +941,8 @@
     return true;
 
   // If not a forward reference, just return it now.
-  if (NumberedMetadata.count(MID)) {
-    Result = NumberedMetadata[MID];
+  if (auto It = NumberedMetadata.find(MID); It != NumberedMetadata.end()) {
+    Result = It->second;
     return false;
   }