samigo: Add info blurb on Submission Status screen to explain when Retake links appear vs. not

While evaluating other issues related to retakes (e.g., SAK-45754, https://sakaiproject.atlassian.net/browse/SAK-44334#icft=SAK-44334), I thought it would be helpful to add an info blurb like the following to the top of the Submission Status screen (in blue info styling):

Tip: If a student has completed all available submissions, you may allow them a retake to submit again.