chore(vrl playground): fix timezone dropdown pop up

[pront]

Summary

Display the available options if a selection wasn't made.

Vector configuration

How did you test this PR?

cdv && cd lib/vector-vrl/web-playground/ && wasm-pack -v  build --target web --out-dir public/pkg && cd public && python3 -m http.server

Select timezone.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Notes

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