docs: remove unused LanguageFilter imports from starting page

[RapidPoseidon]

The Audio and Text tabs of the docs landing page import LanguageFilter but never use it — leftovers from when these examples used the deprecated order API, which took a filters= argument.

create_compare_job_definition has no filters parameter; in the Jobs model, annotator filtering lives on the audience (audience.filter([LanguageFilter(["en"])]), documented in docs/audiences.md). The dangling import points readers at a parameter that does not exist on the job path.

This came out of investigating why a customer on the latest SDK (3.19.2) reached for create_compare_order instead of a job definition: they needed an English-only audience, and filters= only exists on the deprecated order API. The unused import here is one of the trails leading there.

Docs-only, two lines. Verified with uv run --group docs mkdocs build — builds clean, remaining warnings are pre-existing and unrelated.

🔗 Session: session-af1a7b32