Hide locality filter dropdown if there are no dropdown options

[terryttsai]

Description of the change

We are launching Idaho without breaking down locality by judicial districts, so hide the locality dropdown option in Idaho.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Configuration change (adjusts configuration to achieve some end related to functionality, development, performance, or security)

Related issues

Closes #582

Checklists

Development

These boxes should be checked by the submitter prior to merging:

• Manual testing against realistic data has been performed locally

Code review

These boxes should be checked by reviewers prior to merging:

• This pull request has a descriptive title and information useful to a reviewer
• This pull request has been moved out of a Draft state, has no "Work In Progress" label, and has assigned reviewers
• Potential security implications or infrastructural changes have been considered, if relevant

[coveralls]

Pull Request Test Coverage Report for Build 2699533585

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 1 of 2 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 83.602%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
spotlight-client/src/LocalityFilterSelect/LocalityFilterSelect.tsx	1	2	50.0%

Totals
Change from base Build 2699521852:	-0.04%
Covered Lines:	2081
Relevant Lines:	2353

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💛 - Coveralls