Update Jira docs to indicate the development panel limitations of which user can do set up

As per https://gitlab.com/gitlab-org/gitlab-ee/issues/8902#note_126433594 and https://gitlab.com/gitlab-org/gitlab-ee/issues/8902#note_126239733, update Jira development panel integration docs:

• The user setting up integration must be a [Owner, Maintainer, etc] of the group.
• When integration is done via the admin settings, integration is still attached to the currently logged in user.