Investigate cause of double URL encoding with `%` character in table names

[GraemeWatt]

A % character in table names appears as %2525 rather than just %25 in the download URL, resulting in a failed download. I wasn't able to easily resolve this issue, so I made a simple replacement using replace('%2525', '%25') in commit d372f3c. This problem of double URL encoding should be investigated more carefully and a better solution should be found.

[GraemeWatt]

The origin of the double URL encoding is in the redirection of the main HEPData web application (code):

                table_name = request.args['table'].replace('%', '%25').replace('\\', '%5C')

The replacement replace('%', '%25') was first introduced in 2018 in commit HEPData/hepdata@5793558. I don't remember the details of why it was needed, but any changes to the redirect URLs would need to be investigated thoroughly to prevent bugs being introduced. For now, the simple correction of the double URL encoding using replace('%2525', '%25') in the hepdata-cli code works well enough.