[FIR] Don't miss RETURN_NOT_ALLOWED

^KT-59914 Fixed

compiler/testData/diagnostics/tests/controlStructures/kt799.fir.kt

@@ -19,7 +19,7 @@ val <!IMPLICIT_NOTHING_PROPERTY_TYPE!>b<!> = <!RETURN_NOT_ALLOWED!>return<!> 1
 val c = doSmth(if (true) 3 else <!RETURN_NOT_ALLOWED!>return<!>)
 
 
-fun f(mi: Int = if (true) 0 else return) {}
+fun f(mi: Int = if (true) 0 else <!RETURN_NOT_ALLOWED!>return<!>) {}
 
 fun doSmth(i: Int) {
 }