Corrected loadImageSeries type hint

[radarhere]

This is part of #8362 - I'm hoping to break down that PR into easier-to-review chunks.

Two changes to loadImageSeries.

Pillow/src/PIL/SpiderImagePlugin.py

Lines 214 to 233 in 0e3f51d

	def loadImageSeries(filelist: list[str] | None = None) -> list[SpiderImageFile] | None:
	"""create a list of :py:class:`~PIL.Image.Image` objects for use in a montage"""
	if filelist is None or len(filelist) < 1:
	return None
	imglist = []
	for img in filelist:
	if not os.path.exists(img):
	print(f"unable to find {img}")
	continue
	try:
	with Image.open(img) as im:
	im = im.convert2byte()
	except Exception:
	if not isSpiderImage(img):
	print(f"{img} is not a Spider image file")
	continue
	im.info["filename"] = img
	imglist.append(im)
	return imglist

1. convert2byte() is a SpiderImageFile method, so the image must be a SPIDER image to call that
2. convert2byte() returns an Image instance, meaning that loadImageSeries returns a list of Images, not SpiderImageFiles.

Pillow/src/PIL/SpiderImagePlugin.py

Line 189 in 0e3f51d

def convert2byte(self, depth: int = 255) -> Image.Image: