Update bmp param text in Cursor.generate_cursor() docstring

Author: tekktrik

adafruit_cursorcontrol/cursorcontrol.py

@@ -228,7 +228,7 @@ def cursor_bitmap(self, bmp):
     def generate_cursor(self, bmp):
         """Generates a cursor icon
         
-        :param ~displayio.Bitmap bmp: Bitmap to use for the cursor
+        :param ~displayio.Bitmap bmp: A Bitmap to use for the cursor
         """
         self._is_deinited()
         self._cursor_grp = displayio.Group(scale=self._scale)