chore(deps): update ubuntu:20.04 docker digest to 6d8d979 (#2710)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| ubuntu | final | digest | `fa17826` -> `6d8d979` |

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docker/worker-base/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM ubuntu:20.04@sha256:fa17826afb526a9fc7250e0fbcbfd18d03fe7a54849472f86879d8bf562c629e
+FROM ubuntu:20.04@sha256:6d8d9799fe6ab3221965efac00b4c34a2bcc102c086a58dff9e19a08b913c7ef
 
 ENV DEBIAN_FRONTEND noninteractive
 RUN apt-get update && apt-get upgrade -y && \