Fixed epub/pdf download links

- They were reported as linking to the 1.12.8 version, when they should
  be linking to the 2.3.2 version.
- Still need to fix the root cause: the script that updates the
  versions!
Ensure download links for epub/pdf only get updated for v2

- The PDF/epub links are only supposed to be for version 2. However, they _were_
  getting updated for _any_ version change, which leads to situations where v1
  links are present (and should not be, as we do not build those artifacts).
  This change adds a conditional to ensure the update only happens for v2.
Merge branch 'hotfix/remove-zf1-epub-links'