update gotestsum to v1.7.0
Same as previous commit, but a release was tagged;
# See the License for the specific language governing permissions and
# limitations under the License.
-GO111MODULE=on go install gotest.tools/gotestsum@1a9438079330f60c1301fdfacafbfac8763214a5
+GO111MODULE=on go install gotest.tools/gotestsum@v1.7.0
