Remove obsolete not_found_msg

Author: danpoe

src/util/sharing_map.h

@@ -564,8 +564,6 @@ class sharing_mapt
     std::set<const void *> &marked,
     bool mark = true) const;
 
-  static const std::string not_found_msg;
-
   // config
   static const std::size_t bits;
   static const std::size_t chunk;
@@ -1290,8 +1288,6 @@ SHARING_MAPT2(optionalt<std::reference_wrapper<const, mapped_type>>)::find(
 
 // static constants
 
-SHARING_MAPT(const std::string)::not_found_msg="key not found";
-
 SHARING_MAPT(const std::size_t)::bits = 30;
 SHARING_MAPT(const std::size_t)::chunk = 3;