8331200: Serial: Remove unused methods in SerialHeap

Reviewed-by: gli, tschatzl

Author: albertnetymk

src/hotspot/share/gc/serial/serialHeap.hpp

@@ -147,9 +147,6 @@ class SerialHeap : public CollectedHeap {
   void post_initialize() override;
 
   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
-  bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
-
-  MemRegion reserved_region() const { return _reserved; }
   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
 
   // Performance Counter support