docs: DOC-262: Add task reservation setting to docs

[caitlinwheeless]

Introducing a new Task Reservation time setting, and needed to give an explanation in the docs.

Change has impacts in these area(s)

(check all that apply)

• [X] Enterprise docs
• [ ] Community docs

[netlify[bot]]

✅ Deploy Preview for label-studio-docs-new-theme ready!

Name	Link
🔨 Latest commit	8ab5dab653507550d6387a0bbb2c326c3a8759d3
🔍 Latest deploy log	https://app.netlify.com/sites/label-studio-docs-new-theme/deploys/673cfdb81617b5000824b18d
😎 Deploy Preview	https://deploy-preview-6688--label-studio-docs-new-theme.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[netlify[bot]]

✅ Deploy Preview for heartex-docs ready!

Name	Link
🔨 Latest commit	8ab5dab653507550d6387a0bbb2c326c3a8759d3
🔍 Latest deploy log	https://app.netlify.com/sites/heartex-docs/deploys/673cfdb8f8b6ec00081c07cb
😎 Deploy Preview	https://deploy-preview-6688--heartex-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.