switch to go.yaml.in/yaml (#1478)

The `gopkg.in/yaml.v3` library has been declared as Unmaintained:

- https://github.com/go-yaml/yaml?tab=readme-ov-file#this-project-is-unmaintained

The YAML org has taken over maintaining it and now publishes it as
`go.yaml.in/yaml`:

- https://github.com/yaml/go-yaml

config/config.go

@@ -17,7 +17,7 @@ import (
 
 	"dario.cat/mergo"
 	"github.com/sirupsen/logrus"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 type C struct {

config/config_test.go

@@ -10,7 +10,7 @@ import (
 	"github.com/slackhq/nebula/test"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"gopkg.in/yaml.v3"
+	"go.yaml.in/yaml/v3"
 )
 
 func TestConfig_Load(t *testing.T) {