Fix links

[hoxbro]

Two things done in this PR;

1. Convert http://datashader.org to https://datashader.org.
2. Try to update failing links.

Commands used for 1: rg -l 'http://datashader.org' | xargs sed -i 's/http:\/\/datashader.org/https:\/\/datashader.org/g'

The commands used for 2:

rg --no-filename --no-line-number --no-ignore --glob '!*.svg' --glob '!CHANGELOG.rst' -o 'https?:\/\/([\w_-]+(?:(?:\.[\w_-]+)+))([\w.,@?^=%&:\/~+#-]*[\w@?^=%&\/~+#-])' | sort | uniq | tee inputs.txt
parallel 'curl --output /dev/null --silent --fail {} -w "%{http_code} %{url}\n" --connect-timeout 10' :::: inputs.txt | tee outputs.txt
cat outputs.txt | grep '^40' 

Output:

404 http://blaze.pydata.org/docs/datashape.html
404 https://docs.rapids.ai/api/cudf/stable/10min.html
404 https://datashader-tiles-testing.s3.amazonaws.com/wald_tiles/
403 https://storage.googleapis.com/tlc-trip-data/2015/
404 https://www.anaconda.com/distribution/