[NI] Fix checks for infix/operator conventions

compiler/testData/diagnostics/tests/operatorsOverloading/kt11300.kt

@@ -1,3 +1,5 @@
+// !WITH_NEW_INFERENCE
+
 class A {
     operator fun get(x: Int): Int = x
     fun set(<!UNUSED_PARAMETER!>x<!>: Int, <!UNUSED_PARAMETER!>y<!>: Int) {} // no `operator` modifier
@@ -5,7 +7,7 @@ class A {
 
 fun main() {
     val a = A()
-    <!OPERATOR_MODIFIER_REQUIRED!>a[1]<!>++
-    <!OPERATOR_MODIFIER_REQUIRED!>a[1]<!> += 3
+    <!OPERATOR_MODIFIER_REQUIRED!>a<!NI;NO_SET_METHOD!>[1]<!><!>++
+    <!OPERATOR_MODIFIER_REQUIRED!>a<!NI;NO_SET_METHOD!>[1]<!><!> += 3
     <!OPERATOR_MODIFIER_REQUIRED!>a[1]<!> = a[1] + 3
 }