update delete grant so it deletes notifs too

[camila-carrillo]

ℹ️ Issue

Closes #382

📝 Description

Write a short summary of what you added. Why is it important? Any member of C4C should be able to read this and understand your contribution -- not just your team members.

Makes sure grant notifications are created and deleted when the corresponding grant is created/deleted. It is important because the two entities should be in sync with each other.

Briefly list the changes made to the code:

1. Added deleteGrantNotifications()
2. Called above in deleteGrantById()
3. Fixed a bug that was causing notifications to overwrite each other. Notifications now follow structure ${grantId}-app-${days} and ${grantId}-report-${index}-${days}.
4. uncommented creategrantnotifications call in addgrant

✔️ Verification

What steps did you take to verify your changes work? These should be clear enough for someone to be able to clone the branch and follow the steps themselves.

Created a grant with an application deadline and at least one report deadline in the near past, opened notification dropdown and made sure correct notifications popped up. Deleted the grant. Ensured notifications also correctly deleted from the dropdown and dynamodb table.

Provide screenshots of any new components, styling changes, or pages.
n/a

Test Changes

If your new feature required some test to be changed or added to fit the new functionality or changes please document these changes here.

🏕️ (Optional) Future Work / Notes

Did you notice anything ugly during the course of this ticket? Any bugs, design challenges, or unexpected behavior? Write it down so we can clean it up in a future ticket!