[NFC][IR] Use emplace instead of insert (#130360)

Preparation for for CFI Index refactoring,
which will fix O(N^2) in ThinLTO indexing.

Author: vitalybuka

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -8077,16 +8077,16 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
     case bitc::FS_CFI_FUNCTION_DEFS: {
       auto &CfiFunctionDefs = TheIndex.cfiFunctionDefs();
       for (unsigned I = 0; I != Record.size(); I += 2)
-        CfiFunctionDefs.insert(
-            {Strtab.data() + Record[I], static_cast<size_t>(Record[I + 1])});
+        CfiFunctionDefs.emplace(Strtab.data() + Record[I],
+                                static_cast<size_t>(Record[I + 1]));
       break;
     }
 
     case bitc::FS_CFI_FUNCTION_DECLS: {
       auto &CfiFunctionDecls = TheIndex.cfiFunctionDecls();
       for (unsigned I = 0; I != Record.size(); I += 2)
-        CfiFunctionDecls.insert(
-            {Strtab.data() + Record[I], static_cast<size_t>(Record[I + 1])});
+        CfiFunctionDecls.emplace(Strtab.data() + Record[I],
+                                 static_cast<size_t>(Record[I + 1]));
       break;
     }