Merge branch '443870-enable-connect-nulls' into 'master'

Connect null data points in Value Stream Dashboard sparklines

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/160444



Merged-by: Enrique Alcántara <ealcantara@gitlab.com>
Approved-by: Diana Zubova <dzubova@gitlab.com>
Co-authored-by: Alex Pennells <apennells@gitlab.com>