Backport PR matplotlib#26237: Update FancyBboxPatch docstring

Author: rcomer

lib/matplotlib/patches.py

@@ -3799,7 +3799,7 @@ def __init__(self, xy, width, height, boxstyle="round", *,
         """
         Parameters
         ----------
-        xy : float, float
+        xy : (float, float)
           The lower left corner of the box.
 
         width : float