Fix typo in vector-heads-tails.py
Remove period from phrase in parenthesis in vector-heads-tails.py gallery example.
@@ -26,7 +26,7 @@ corresponding module.
In the following we use the :meth:`pygmt.Figure.plot` method to plot vectors
with individual heads and tails. We must specify the modifiers (together with
the vector type, here ``v``, see also
-:doc:`Vector types documentation </gallery/line/vectors>`.)
+:doc:`Vector types documentation </gallery/line/vectors>`)
by passing the corresponding shortcuts to the ``style`` parameter.
"""
