[FIR] Java super-type arguments are now handled as flexible

compiler/testData/loadJava/compiledJava/modality/ModalityOfFakeOverrides.fir.txt

@@ -1,4 +1,4 @@
-public open class ModalityOfFakeOverrides : R|java/util/AbstractList<kotlin/String>| {
+public open class ModalityOfFakeOverrides : R|java/util/AbstractList<ft<kotlin/String, kotlin/String?>!>| {
     @R|java/lang/Override|() @R|org/jetbrains/annotations/NotNull|() public open operator fun get(index: R|kotlin/Int|): R|kotlin/String|
 
     @R|java/lang/Override|() public open operator fun size(): R|kotlin/Int|