Update CHANGELOG.md

[eliasyishak]

Related to previous PR:

• Setting up package:unified_analytics within devtools #7084

This adds an entry into the CHANGELOG.md to highlight that we are adding a new parameter to ServerApi.handle to accept analytics.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or there is a reason for not adding tests.

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