Deprecate MDTranslator data.gov service

## User Story

Only when all ISO sources are deprecated, or replacement translation is in place.

In order to [goal], [stakeholder] wants [change].

## Acceptance Criteria

[ACs should be clearly demoable/verifiable whenever possible. Try specifying them using [BDD](https://en.wikipedia.org/wiki/Behavior-driven_development#Behavioral_specifications).]

- [ ] GIVEN [a contextual precondition] \
[AND optionally another precondition] \
WHEN [a triggering event] happens \
THEN [a verifiable outcome] \
[AND optionally another verifiable outcome]

## Background

[Any helpful contextual notes or links to artifacts/evidence, if needed]

## Security Considerations ([required](https://nvd.nist.gov/800-53/Rev4/control/CM-4))

[comment]: # "Our SSP says 'The Data.gov team ensures security implications are considered as part of the agile requirements refinement process by including a section in the issue template used as a basis for new work.' so please don't remove this section without care."
[Any security concerns that might be implicated in the change. "None" is OK, just be explicit here!]

## Sketch

[Notes or a checklist reflecting our understanding of the selected approach]

The issue names no files, tests, or entry points. First identify the MDTranslator data.gov service and inventory the ISO sources and any replacement translation path; done requires a verified deprecation plan showing that the stated condition is met.

Written by the indexing model from the issue text.