Seek past the data when skipping a PSD layer

[radarhere]

Resolves #7482

When reading through layers in a PSD, Pillow skips layers that have more than 4 channels.

Pillow/src/PIL/PsdImagePlugin.py

Lines 184 to 192 in a10dec0

	# image info
	mode = []
	ct_types = i16(read(2))
	types = list(range(ct_types))
	if len(types) > 4:
	continue
	for _ in types:
	type = i16(read(2))

However, when doing so, there is only a continue. It ignores the fact that there is still data in this file relating to the current layer, that we would have started reading otherwise.

This PR skips past the rest of the layer. I created a test image in GIMP, using a layer mask as the fifth channel for a layer, and then adding another layer after that.