[FIR] Fix missing receiver type if anonymous function without label

compiler/testData/diagnostics/tests/callableReference/function/extensionToSupertype.fir.kt

@@ -13,7 +13,7 @@ fun take(f: (A) -> Unit) {}
 fun take(f: () -> Unit) {}
 
 fun test() {
-    B::foo checkType { <!UNRESOLVED_REFERENCE!>_<!><KFunction1<B, Unit>>() }
+    B::foo checkType { _<KFunction1<B, Unit>>() }
 
     <!INAPPLICABLE_CANDIDATE!>take<!>(B::foo)
 }

compiler/testData/diagnostics/tests/callableReference/function/fakeOverrideType.fir.kt

@@ -11,7 +11,7 @@ class B : A() {
 
 
 fun test() {
-    B::foo checkType { <!UNRESOLVED_REFERENCE!>_<!><KFunction2<B, String, String>>() }
+    B::foo checkType { _<KFunction2<B, String, String>>() }
 
     <!INAPPLICABLE_CANDIDATE!>(B::hashCode)("No.")<!>
 }