Broken links in Save Code Now browse request pages

The links to the archived projects in https://archive.softwareheritage.org/save/#requests produce an error 400 "BadInputExc: Unable to parse date string" See for example:

• https://archive.softwareheritage.org/browse/origin/?origin_url=https://github.com/torvalds/linux&timestamp=2020-08-24T09:22:41.181224+00:00

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Migrated from T2532 (view on Phabricator)