Strip away copyrighted ICC profile

Same as https://github.com/aws/aws-sdk-php/pull/313

While searching for embedded non-free ICC profile:

	find . -regextype posix-extended -iregex '.*\.(jpg|png|tif|ico)' \
		-exec sh -c 'identify -verbose "$0" \
		| grep -i copyright && echo "$0"' {} \;

`docs/_static/logo.png` showed up. The proposed file just removes the embedded non-free ICC profile:

	exiftool -icc_profile"-<=" docs/_static/logo.png

It makes the file a bit smaller, without changing the image.

https://lists.debian.org/debian-devel/2014/05/msg00339.html and the whole thread provide more information.