Apparently, GitHub docs were changes to _assume_ a default doc version
of 'free-pro-team@latest', and drop support for specifying that
explicitly.

Additionally, remove the '/en' locale specifier, so the browser can
negotiate the appropriate one for every user.

Changes were done mechanically using
```bash
for f in $(rg '@latest' -l) ; do
    sed --in-place=.doc \
        -e 's:docs.github.com/en/free-pro-team@latest/:docs.github.com/:g' \
        $f
done
```