Fix dependabot alert for indirect test dependency

Fix dependabot alert for the gopkg.in/yaml.v3 dependency, a transitive dependency of the github.com/stretchr/testify package.
The package is used only for assertions in test files. Requiring the go-tuple package does not transitively require github.com/stretchr/testify nor gopkg.in/yaml.v3 at all, and specifically not it's vulnerable version.

What's Changed

• Upgrade stretchr/testify dependency to fix security issue in yaml.v3 by @barweiss in #23

Full Changelog: v1.1.1...v1.1.2