[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.fir.kt

@@ -0,0 +1,11 @@
+interface A {
+    fun f(): String = "string"
+}
+
+open class B {
+    open fun f(): CharSequence = "charSequence"
+}
+
+class C : B(), A
+
+val obj: A = object : B(), A {}