[Feature flag] Enable NDJSON feature flags by default for Project import and export

What

Enable :project_import_ndjson feature flag by default Enable :project_export_as_ndjson feature flag by default

Owners

• Team: memory_team
• Most appropriate slack channel to reach out to: #g_memory
• Best individual to reach out to: @nmilojevic1

Expectations

Project import supports importing exports in both legacy and ndjson format, so it's safe to leave it and enable it by default. Once this goes live, we should disable project_export_as_ndjson for Project export, until the official release of the feature (22nd, release of %13.0)

Beta groups

Roll Out Steps

• Enable on staging
• Test and measure on staging #215007 (closed), #215004 (closed)
• Ensure that documentation has been updated #215125 (closed) | !31234 (merged)
• We disable project_export_as_ndjson (only exporter!) of ndjson till the official release of feature (22nd as this is release date of %13.0)
• We can selectively enable project_export_as_ndjson for a few test namespaces from Beta groups, to confirm it is working. We don't want to break the ability to import into GitLab.com until 13.0 is officially released.
• Re-enable project_export_as_ndjson FF on GitLab.com on 22th.