Add timezone fix to documentation (fixed for CO, as reference)

[victor-chaparro]

Problem statement

We are no longer able to use the setting convertDateTimeToReceiverLocalTimezone under the receiver translation settings. To support this setting we have developed an enrichment schema that allows us to convert all datetimes in a FHIR bundle to a specific timezone.
The documentation for migrating and onboarding receivers needs to be update to take this into account.

What you need to know

Documentation that needs to be updated:

• https://github.com/CDCgov/prime-reportstream/blob/main/prime-router/docs/onboarding-users/migrating-receivers.md
• https://github.com/CDCgov/prime-reportstream/blob/main/prime-router/docs/onboarding-users/receivers.md

The documentation needs to mention how to use the new enrichment schema and how to create a new one if necessary.

Acceptance criteria

• Documentation is updated with new process on using enrichment schemas to set a receiver's timezone