Bump gds-api-adapters to 4.3.0.

Two main new features: the ability to traverse paginated responses in
the content API and the ability to follow redirect responses from
services, so we can change URLs in services without needing an immediate
version bump in every application.

See https://github.com/alphagov/gds-api-adapters/compare/v4.1.3...v4.3.0
for full changes.