Add note for reminders to the dev on call coordinator process

Why is this change being made?

When coordinators sign up well in advance, they may forget or miss going through the assignment exercise the month prior. This MR adds a substep to the instructions proposing to the coordinator to set reminders and/or the due date on the issue.

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • The when to get approval handbook section explains the workflow in more detail
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