Removed documentation of unused argument

[radarhere]

I see no reason to mention mode in the following docstring

Pillow/src/PIL/ImageFont.py

Lines 156 to 172 in 3c2d36e

	def getbbox(self, text, *args, **kwargs):
	"""
	Returns bounding box (in pixels) of given text.
	.. versionadded:: 9.2.0
	:param text: Text to render.
	:param mode: Used by some graphics drivers to indicate what mode the
	driver prefers; if empty, the renderer may return either
	mode. Note that the mode is always a string, to simplify
	C-level implementations.
	:return: ``(left, top, right, bottom)`` bounding box
	"""
	_string_length_check(text)
	width, height = self.font.getsize(text)
	return 0, 0, width, height