Remove unused template of function for_each_slot_prefix()

for_each_slot_prefix() is not used anywhere with two arguments

libgnucash/engine/kvp-frame.hpp

@@ -235,20 +235,6 @@ struct KvpFrameImpl
     KvpValue * set_impl (std::string const &, KvpValue *) noexcept;
 };
 
-template<typename func_type>
-void KvpFrame::for_each_slot_prefix(std::string const & prefix,
-        func_type const & func) const noexcept
-{
-    std::for_each (m_valuemap.begin(), m_valuemap.end(),
-        [&prefix,&func](const KvpFrameImpl::map_type::value_type & a)
-        {
-            /* Testing for prefix matching */
-            if (strncmp(a.first, prefix.c_str(), prefix.size()) == 0)
-                func (&a.first[prefix.size()], a.second);
-        }
-    );
-}
-
 template<typename func_type, typename data_type>
 void KvpFrame::for_each_slot_prefix(std::string const & prefix,
         func_type const & func, data_type & data) const noexcept