Repo gardening: update auto-labeling rules for Boost

[jeherve]

Proposed changes:

Boost modules were moved to a features/ directory in #22163, but this task wasn't updated accordingly. This should fix things.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

• p1675960331034229/1675957795.951349-slack-CBG1CP4EN

Does this pull request change what data or activity we track or use?

• No

Testing instructions:

• Not much to test here, this will change how labels are applied in future PRs touching Boost features.

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
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• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
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• ✅ Add changelog entries to affected projects
  

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Then, add the "[Status] Needs Team review" label and ask someone from your team review the code.
Once you’ve done so, switch to the "[Status] Needs Review" label; someone from Jetpack Crew will then review this PR and merge it to be included in the next Jetpack release.

[sergeymitr]

LGTM 👍 🚢