release notes: schema tracking no longer experimental

[deepthi]

Description

We forgot to document this in the summary release notes.

Related Issue(s)

#10595

Checklist

• "Backport me!" label has been added if this change should be backported
• Tests were added or are not required
• Documentation was added or is not required Schema Tracking is GA in v14+ website#1078

Deployment Notes

[github-actions]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• If this is a change that users need to know about, please apply the release notes (needs details) label so that merging is blocked unless the summary release notes document is included.
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Bug fixes

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Non-trivial changes

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New/Existing features

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Backward compatibility

• Protobuf changes should be wire-compatible.
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