[TableGen] Avoid assignmentInAssert warning (#139715)

ExpectedID should be optimized out anyway if built without assertions
because nothing reads its value.

Fixes #90327

llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp

diff --git a/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp b/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp
index 36c0cf5..d11812b 100644
--- a/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp
@@ -2610,9 +2610,9 @@
     // That way we can just get the RuleID from the enum by subtracting
     // (GICXXPred_Invalid + 1).
     unsigned ExpectedID = 0;
-    (void)ExpectedID;
     for (const auto &ID : keys(AllCombineRules)) {
-      assert(ExpectedID++ == ID && "combine rules are not ordered!");
+      ++ExpectedID;
+      assert(ExpectedID == ID && "combine rules are not ordered!");
       OS << "  " << getIsEnabledPredicateEnumName(ID) << EnumeratorSeparator;
       EnumeratorSeparator = ",\n";
     }