[Presburger] Avoid repeated hash lookups (NFC) (#107426)

Author: kazutakahirata

mlir/lib/Analysis/Presburger/IntegerRelation.cpp

@@ -2367,10 +2367,8 @@ bool IntegerRelation::removeDuplicateConstraints() {
   hashTable.insert({row, 0});
   for (unsigned k = 1; k < ineqs; ++k) {
     row = getInequality(k).drop_back();
-    if (!hashTable.contains(row)) {
-      hashTable.insert({row, k});
+    if (hashTable.try_emplace(row, k).second)
       continue;
-    }
 
     // For identical cases, keep only the smaller part of the constant term.
     unsigned l = hashTable[row];