Managed Go version is not used in CircleCI

[tabboud]

The Go version for this library is managed by Excavator via the .palantir/go-version file, but the CircleCI config does not respect this version and must be manually updated. As a result, the versions are lagging behind what the expected managed version is and any follow on excavators that update dependencies and manage the Go version end up failing due to the misaligned Go version.