FIR: Support flexible types in getErasedVersionOfFirstUpperBound

compiler/testData/diagnostics/tests/platformTypes/rawTypes/nonTrivialErasure.fir.kt

@@ -22,7 +22,7 @@ val strList: List<String> = null!!
 fun main() {
     val rawA = Test.rawAField
     rawA.first = Test.rawAField.second
-    Test.rawAField.second = rawA.first.<!INAPPLICABLE_CANDIDATE!>second<!>
+    Test.rawAField.second = rawA.first.second
 
     rawA.listOfDoubles = strList
     rawA.listOfDoubles = "" // first should be List

compiler/testData/diagnostics/tests/platformTypes/rawTypes/rawTypeInUpperBound.fir.kt

@@ -27,12 +27,12 @@ public class Test {
 
 fun foo(x: B<*>) {
     // TODO: x.foo() now is flexible type instead of raw, because of captured type approximation
-    val q: MutableList<String> = x.foo().<!INAPPLICABLE_CANDIDATE!>getChildrenStubs<!>()
+    val q: MutableList<String> = x.foo().getChildrenStubs()
 
     // Raw(B).field erased to A<Any!>..A<out Any!>?
     Test.rawB.field = A<String>()
     val anyA: A<Any> = Test.rawB.field
 
-    Test.rawB.field.<!INAPPLICABLE_CANDIDATE!>consume<!>("")
-    val y: Any = Test.rawB.field.<!INAPPLICABLE_CANDIDATE!>produce<!>()
+    Test.rawB.field.consume("")
+    val y: Any = Test.rawB.field.produce()
 }