Psi2ir: fix function type check for fun interface conversion

Parameter of a synthetic SAM adapter always has a function type (not a
subtype). Checking for the subtypes broke the case from KT-46908, where
fun interface is itself a subtype of a function type.

 #KT-46908 Fixed

compiler/tests-gen/org/jetbrains/kotlin/ir/KlibTextTestCaseGenerated.java

@@ -1636,6 +1636,11 @@ public class KlibTextTestCaseGenerated extends AbstractKlibTextTestCase {
                 runTest("compiler/testData/ir/irText/expressions/funInterface/castFromAny.kt");
             }
 
+            @TestMetadata("functionSupertype.kt")
+            public void testFunctionSupertype() throws Exception {
+                runTest("compiler/testData/ir/irText/expressions/funInterface/functionSupertype.kt");
+            }
+
             @TestMetadata("partialSam.kt")
             public void testPartialSam() throws Exception {
                 runTest("compiler/testData/ir/irText/expressions/funInterface/partialSam.kt");