Remove Disused Backfill Containers

[ACoullard]

Summary
A few of the backfill containers (backfill users and backfill notification) are still being run by the docker compose despite being no longer necessary.

Work Detail
Remove the docker compose entries, the package.json script entries, and the corresponding typescript scripts referenced by the package.json

Resources

package.json
scripts/firebase-admin/backfillNotificationFrequency.ts
scripts/firebase-admin//backfillUserEmails.ts