Fix incorrect condition in CheckIrElementVisitor.ensureTypeIs

Apparently it has no effect on behavior of tests because no backend uses
the checkTypes mode of IR validation

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt

@@ -53,8 +53,7 @@ class CheckIrElementVisitor(
         if (!config.checkTypes)
             return
 
-        // TODO: compare IR types instead.
-        if (expectedType.isEqualTo(type)) {
+        if (!expectedType.isEqualTo(type)) {
             reportError(this, "unexpected expression.type: expected $expectedType, got ${type.render()}")
         }
     }