libexpr: Remove non-const iterators of Bindings

src/libexpr/attr-set.cc

@@ -35,8 +35,7 @@ Value & BindingsBuilder::alloc(std::string_view name, PosIdx pos)
 
 void Bindings::sort()
 {
-    if (size_)
-        std::sort(begin(), end());
+    std::sort(attrs, attrs + size_);
 }
 
 Value & Value::mkAttrs(BindingsBuilder & bindings)

src/libexpr/include/nix/expr/attr-set.hh

@@ -81,8 +81,6 @@ public:
         return !size_;
     }
 
-    typedef Attr * iterator;
-
     typedef const Attr * const_iterator;
 
     void push_back(const Attr & attr)
@@ -108,16 +106,6 @@ public:
         return nullptr;
     }
 
-    iterator begin()
-    {
-        return &attrs[0];
-    }
-
-    iterator end()
-    {
-        return &attrs[size_];
-    }
-
     const_iterator begin() const
     {
         return &attrs[0];