fix constructors.rst

doc/manual/constructors.rst

@@ -586,7 +586,7 @@ to another, you should probably define a ``convert`` method instead.
 On the other hand, if your constructor does not represent a lossless
 conversion, or doesn't represent "conversion" at all, it is better
 to leave it as a constructor rather than a ``convert`` method.  For
-example, the ``Array{Int}`` constructor creates a zero-dimensional
+example, the ``Array{Int}()`` constructor creates a zero-dimensional
 ``Array`` of the type ``Int``, but is not really a "conversion" from
 ``Int`` to an ``Array``.