Create animation.py

Updated grammar to reflect more common usage of output vs outputted (see https://books.google.com/ngrams/graph?content=was+output%2Cwas+outputted&year_start=1800&year_end=2000&corpus=15&smoothing=3&direct_url=t1%3B%2Cwas%20output%3B%2Cc0%3B.t1%3B%2Cwas%20outputted%3B%2Cc0)

Author: diegosolano

lib/matplotlib/animation.py

@@ -882,7 +882,7 @@ def __del__(self):
                 'Animation was deleted without rendering anything. This is '
                 'most likely not intended. To prevent deletion, assign the '
                 'Animation to a variable, e.g. `anim`, that exists until you '
-                'have outputted the Animation using `plt.show()` or '
+                'output the Animation using `plt.show()` or '
                 '`anim.save()`.'
             )