Backport PR matplotlib#32179: Document and fix AngleAnnotation constructor default case of using the current Axes (matplotlib#32180)

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Author: meeseeksmachine

galleries/examples/text_labels_and_annotations/angle_annotation.py

@@ -91,7 +91,7 @@ def __init__(self, xy, p1, p2, size=75, unit="points", ax=None,
             * "axes min", "axes max": minimum or maximum of relative Axes
               width, height
 
-        ax : `matplotlib.axes.Axes`
+        ax : `matplotlib.axes.Axes`, default: current Axes
             The Axes to add the angle annotation to.
 
         text : str
@@ -128,7 +128,7 @@ def __init__(self, xy, p1, p2, size=75, unit="points", ax=None,
                        xytext=(0, 0), textcoords="offset points",
                        annotation_clip=True)
         self.kw.update(text_kw or {})
-        self.text = ax.annotate(text, xy=self._center, **self.kw)
+        self.text = self.ax.annotate(text, xy=self._center, **self.kw)
 
     def get_size(self):
         factor = 1.