Update dependency @types/chai to v4.3.0

Editor assessment

Updating @types/chai to v4.3.0 states the dependency and target version precisely, and chore(deps) matches the maintenance bump in type and scope. The subject fully identifies the change, so no diff is needed to know what happened. There is no body, appropriate for a type-definition update, and no footers appear, none being owed. Hygiene is clean: imperative mood, no trailing period, short specific subject, no ticket junk, no pasted material. A routine dependency update expressed in one complete line — exactly the communication this change requires.