Fix spelling.

A quick googling hasn't shown any use of "co-erce"; MW (e.g.) only gives
"coerce".

Author: anntzer

lib/matplotlib/axes/_axes.py

@@ -1629,7 +1629,7 @@ def plot(self, *args, scalex=True, scaley=True, data=None, **kwargs):
     def plot_date(self, x, y, fmt='o', tz=None, xdate=True, ydate=False,
                   **kwargs):
         """
-        Plot co-ercing the axis to treat floats as dates.
+        Plot coercing the axis to treat floats as dates.
 
         .. admonition:: Discouraged