Remove `@inngest/eslint-plugin` alpha warnings; it's in use

[jpwilliams]

Summary

Removes the warning in the @inngest/eslint-plugin package README that states it's in alpha; it's being used and is working.

Checklist

• [ ] ~Added a docs PR that references this PR~ N/A
• [ ] ~Added unit/integration tests~ N/A
• [x] Added changesets if applicable

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 11c943519a82175bd741ac0a99c075c5916abde5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ---------------------- | ----- | | @inngest/eslint-plugin | Patch |

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