[FIR] 2/2 Cleanup: drop no longer necessary FirActualCallableDeclarationChecker

It became possible to drop it after KT-62590. Now, on a frontend, the
return type check is part of a common AbstractExpectActualChecker logic

Change in nestedAnnotationClassViaActualTypealias.fir.kt aligns the
behaviour with K1. KT-61964

Review: https://jetbrains.team/p/kt/reviews/12750/timeline

compiler/testData/diagnostics/tests/multiplatform/defaultArguments/nestedAnnotationClassViaActualTypealias.fir.kt

@@ -11,4 +11,4 @@ class DefaultArgsInNestedClassImpl {
 }
 
 // Incompatible because of bug KT-31636
-actual typealias DefaultArgsInNestedClass = DefaultArgsInNestedClassImpl
+actual typealias <!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>DefaultArgsInNestedClass<!> = DefaultArgsInNestedClassImpl

compiler/testData/diagnostics/tests/multiplatform/hmpp/kt57320.fir.kt

@@ -34,7 +34,7 @@ interface KotlinXStringDemoInterface {
 // FILE: StringDemoInterface.kt
 actual typealias StringDemoInterface = KotlinXStringDemoInterface
 
-actual fun StringDemoIn<!EXPECT_ACTUAL_INCOMPATIBILITY!>terface.<!ACTUAL_WITHOUT_EXPECT("actual fun StringDemoInterface.plusK(): <ERROR TYPE REF: Unresolved name: value>; The following declaration is incompatible:    expect fun StringDemoInterface.plusK(): String")!>plusK<!>() = <!EXPECT_CLASS_AS_FUNCTION!>StringValue<!>(value).plus("K")<!>.<!UNRESOLVED_REFERENCE!>value<!>
+actual fun StringDemoIn<!EXPECT_ACTUAL_INCOMPATIBILITY!>terface.<!ACTUAL_WITHOUT_EXPECT("actual fun StringDemoInterface.plusK(): <ERROR TYPE REF: Unresolved name: value>; The following declaration is incompatible because return type is different:    expect fun StringDemoInterface.plusK(): String")!>plusK<!>() = <!EXPECT_CLASS_AS_FUNCTION!>StringValue<!>(value).plus("K")<!>.<!UNRESOLVED_REFERENCE!>value<!>
 
 // FILE: main.kt
 class StringDemo(override val value: String) : StringDemoInterface