[vm] Cleanup dead code

TEST=ci

Change-Id: I0ba2ec4a46b81f4efcbf3e516a70a3c2b40bb74a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/493861
Auto-Submit: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

runtime/vm/compiler/stub_code_compiler.cc

@@ -679,9 +679,6 @@ static void BuildInstantiateTypeParameterStub(Assembler* assembler,
                              InstantiateTypeABI::kResultTypeReg);
   }
 
-  __ LoadClassId(InstantiateTypeABI::kScratchReg,
-                 InstantiateTypeABI::kResultTypeReg);
-
   switch (nullability) {
     case Nullability::kNonNullable:
       __ Ret();

runtime/vm/object.cc

@@ -11513,7 +11513,6 @@ const char* Function::UserVisibleNameCString() const {
   if (FLAG_show_internal_names) {
     return String::Handle(name()).ToCString();
   }
-  is_extension_type_member();
   return String::ScrubName(String::Handle(name()),
                            is_extension_member() || is_extension_type_member());
 }