4743: change mobile lighthouse letters client id to match new key

[kpethtel]

Summary

• Changes mobile lighthouse letters config to use new key client id

Related issue(s)

https://app.zenhub.com/workspaces/va-mobile---backend-61d75d03a7505500147ec7f6/issues/gh/department-of-veterans-affairs/va-mobile-app/4743

Testing done

Screenshots

Note: Optional

What areas of the site does it impact?

None at this time because we're not yet using this api key.

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature

Requested Feedback

[kpethtel]

We're working with the letters team and they're adding their own keys which will contain all of this info. We only need client id. The plan is to use our client id when making calls so that the lighthouse team knows who's using the API.