Thanks German and Koen.
As part of the downloads site makeover, we decided NOT to have a page on the downloads site listing all the links https://download.moodle.org/langpack/2.7/, https://download.moodle.org/langpack/2.6/ etc. and instead include language packs links on release pages such as https://download.moodle.org/releases/latest/, since normally language packs are installed from within Moodle, and there is no need to browse language packs by version.
However, thanks for pointing out that we need to redirect download.moodle.org/langpack appropriately. I created MDLSITE-3394 for it.