chore: update changelog

Summary

• LIMIT: !1185 (merged)

• SUBSTR: sbroad!501 (merged)

Pgproto:

• Parameters types via cast and postgres cast notation: !1071 (merged)

• Tab-completion for psql: !1195 (merged)

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• Cherry-pick to: none
• Docs follow-up: docs#329 (closed), docs#333 (closed)