Remove next-release changesets

[rosetta-livekit-bot]

Ports livekit/agents#6054 to agents-js by removing the pending next-release changeset markdown inputs from the 1.5.0 branch.\n\nValidation:\n- git diff --check\n- pnpm exec changeset status --since 1.5.0

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Ported from livekit/agents#6054

Original PR description

Summary

The .github/next-release changeset process is no longer used: the publish workflow only ever invoked update_versions.py with --ignore-changesets (uniform bumps) or --pre, so the changeset-driven path was dead code.

• Delete .github/next-release/ (one leftover changeset)
• Remove parse_changeset_file / load_changesets / the changeset-driven bump path from update_versions.py; the uniform bump becomes the only normal-release path and the --ignore-changesets flag is gone
• Drop the flag from publish.yml invocations

Verified: --help works, no remaining references to changesets or next-release.

🤖 Generated with Claude Code

[changeset-bot]

⚠️ No Changeset found

Latest commit: a0fcec2

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.