[FIR] Mark more calls origin as OPERATOR

compiler/testData/diagnostics/tests/j+k/collectionOverrides/irrelevantImplMutableListKotlin.fir.kt

@@ -99,7 +99,8 @@ public class A extends AImpl implements List<String> {
 
 fun main() {
     val x = X()
-    x[0]
+    //todo get only one candidate - AImpl.get, no kotlin.collection.List for some reason
+    <!OPERATOR_MODIFIER_REQUIRED!>x[0]<!>
     x.size
     x.remove("")
     x.remove(1)