oqgraph: remove clang warnings

-Wdeprecated-copy-with-user-provided-copy was causing a few errors on
things that where defined in a way that was implicit. By removing code
it now compiles without warnings.

tested with fc38 / clang-16

storage/oqgraph/graphcore.cc

@@ -146,17 +146,6 @@ namespace open_query
       HAVE_EDGE = 4,
     };
 
-    // Force assignment operator, so we can trace through in the debugger
-    inline reference& operator=(const reference& ref) 
-    {    
-      m_flags = ref.m_flags;
-      m_sequence = ref.m_sequence;
-      m_vertex = ref.m_vertex;
-      m_edge = ref.m_edge;
-      m_weight = ref.m_weight;
-      return *this;
-    }
-
     inline reference()
       : m_flags(0), m_sequence(0),
         m_vertex(graph_traits<Graph>::null_vertex()),

storage/oqgraph/oqgraph_judy.h

@@ -107,7 +107,6 @@ namespace open_query
       size_type n;
     };
 
-    reference operator[](size_type n) { return reference(*this, n); }
     bool operator[](size_type n) const { return test(n); }
 
     size_type find_first() const;

storage/oqgraph/oqgraph_shim.h

@@ -60,9 +60,6 @@ namespace oqgraph3
     edge_iterator(const graph_ptr& graph, size_t offset=0)
       : _graph(graph)
       , _offset(offset) { }
-    edge_iterator(const edge_iterator& pos)
-      : _graph(pos._graph)
-      , _offset(pos._offset) { }
     value_type operator*();
     self& operator+=(size_t n) { _offset+= n; return *this; }
     self& operator++() { ++_offset; return *this; }