Fix remaining terraform errors caused by LZ infrastructure merge

[aloftus23]

🗣 Description

This fixes the 3 terraform errors below:

1. Makes sure we aren't changing the volume of the ELK EC2 (reminder this is only created in the DMZ)
2. Makes sure the cognito email is correct and verified (was being changed to staging-cd.crossfeed... which is not verified. Keep it staging.crossfeed...)
3. MariaDB does not support IAM Database Authentication, so sets the iam_database_authentication_enabled parameter to false

💭 Motivation and context

🧪 Testing

Passes pre-commits and github checks

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[Matthew-Grayson]

🚀

[nickviola]

LGTM