test_npm: Adapt content_get_metadata call to content_get
Related to T645
Test Plan
tox (failing until storage release > 0.12)
Migrated from D3735 (view on Phabricator)
Staging instance, all changes can be removed at any time
Related to T645
tox (failing until storage release > 0.12)
Migrated from D3735 (view on Phabricator)