Chore: Remove duplicate interpolateString test (#29941)

pkg/api/pluginproxy/ds_auth_provider_test.go

-package pluginproxy
-
-import (
-	"testing"
-
-	. "github.com/smartystreets/goconvey/convey"
-)
-
-func TestDsAuthProvider(t *testing.T) {
-	Convey("When interpolating string", t, func() {
-		data := templateData{
-			SecureJsonData: map[string]string{
-				"Test": "0asd+asd",
-			},
-		}
-
-		interpolated, err := interpolateString("{{.SecureJsonData.Test}}", data)
-		So(err, ShouldBeNil)
-		So(interpolated, ShouldEqual, "0asd+asd")
-	})
-}