build(deps): bump ubuntu from 20.04 to 22.04 in /docker/test-shadow

Bumps ubuntu from 20.04 to 22.04.

---
updated-dependencies:
- dependency-name: ubuntu
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
(cherry picked from commit 5a1d22a)

docker/test-shadow/Dockerfile

@@ -15,7 +15,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License
 
-FROM ubuntu:20.04
+FROM ubuntu:22.04
 
 MAINTAINER Datawire <flynn@datawire.io>
 LABEL PROJECT_REPO_URL         = "git@github.com:datawire/ambassador.git" \