Remove feature flag and enable user activity indicator once ohsome db is in production

[matthiasschaub]

If possible revert these commits:

• bd9de95 - chore: update TODO comments
• bb3d9e4 - refactor: disable user-activity indicators if ohsomedb is disabled
• c8a81b7 - refactor: put ohsomedb feature behind a feature flag

Or search for this todo comment:

# TODO(feature-flag): remove once once ohsome db is in production