Update deposit through the deposit client no longer works

Updating a deposit in "done" state no longer works:

client side:

swh deposit upload --url https://deposit.staging.swh.network \
  --username swh \
  --password $(swhpass ls operations/deposit.softwareheritage.org/http-auth/swh | head -1) \
  --deposit-id 37 \
  --swhid swh:1:dir:2ddb1f0122c57c8479c28ba2fc973d18508e6420 \
  --metadata ../deposit-swh.update-metadata.xml

Server side (staging):

Jan 05 16:14:42 deposit python3[1392754]: 2021-01-05 16:14:42 [1392754] gunicorn.access:INFO 127.0.0.1 - swh [05/Jan/2021:16:14:42 +0000] "PUT /1/swh/37/metadata/ HTTP/1.1" 405 294 "-" "swh-deposit/0.9.1.dev2+g00d315ec.d20210105"

Which is surprising considering [1]

• [1] https://forge.softwareheritage.org/source/swh-deposit/browse/master/swh/deposit/api/urls.py$45-52

---

Migrated from T2929 (view on Phabricator)