JVM_IR: remove an assertion that triggers due to a frontend bug

compiler/testData/codegen/box/controlStructures/ifIncompatibleBranches.kt

@@ -0,0 +1,10 @@
+fun box(): String {
+    var s = "2"
+    var res = "Fail"
+    if (s == "1") {
+        false
+    } else if (s == "2") {
+        res = "OK"
+    }
+    return res
+}