Fix switching between different ADR modes

[ryaplots]

Summary

This PR fixes the error found in testing in this comment: https://github.com/TheThingsIndustries/lorawan-stack-support/issues/1064#issuecomment-2082120568, point 7.

Changes

• Check if dynamic is an adr before logic

Testing

1. Login into the console
2. Go to any device/create and application and device
3. Go to device settings, to Network Server section and open the collapsed "Avanced MAC settings" section.
4. Select ADR Dynamic mode.
5. Uncheck Use default settings for number of retransmissions
6. Click Add data rate specific override and add the data rate and NbTrans
7. Then save changes. The specific override should be saved.
8. Select ADR disabled and save changes.
9. Refresh the page and see that the ADR mode is disabled.

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Testing: The steps/process to test this feature are clearly explained including testing for regressions.
• Infrastructure: If infrastructural changes (e.g., new RPC, configuration) are needed, a separate issue is created in the infrastructural repositories.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.