Fix word_shift_right bug

include/bitlib/bit-algorithms/bit_algorithm_details.hpp

@@ -288,7 +288,6 @@ RandomAccessIt word_shift_left(RandomAccessIt first,
     if (n >= distance(first, last)) return first;
     RandomAccessIt mid = first + n;
     auto ret = std::move(mid, last, first);
-    //std::fill(ret, last, 0);
     return ret;
 }
 
@@ -305,12 +304,7 @@ ForwardIt word_shift_right_dispatch(ForwardIt first,
         auto d = distance(first, last);
     if (n <= 0) return first;
     if (n >= d) return last;
-    ForwardIt it = first;
-    std::advance(it, d-n);
-    std::rotate(first, it, last);
-    it = first;
-    std::advance(it, n);
-    std::fill(first, it, 0);
+    std::move_backward(first, last, last - n);
     return std::next(first, n);
 }