Dependency updates

[lognaturel]

Closes #497

What has been done to verify that this works as intended?

• Ran the updated smtp image on Digital Ocean and verified email sending attempts work the same way
• Reviewed the nginx-certbot diff and verified that there are no changes to redirector.conf. Put upgrade on dev server

Changes are fairly minimal for the nginx-certbot image, there just is one technically breaking change.

Why is this the best possible solution? Were any other approaches considered?

Uses latest versions.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Neither upgrade looks very risky.

Does this change require updates to documentation? If so, please file an issue here and include the link below.

No.

Before submitting this PR, please make sure you have:

• branched off and targeted the next branch OR only changed documentation/infrastructure (master is stable and used in production)
• verified that any code or assets from external sources are properly credited in comments or that everything is internally sourced