Bump ubuntu from 99c3519 to 278628f in /images/toolbox (#44)

Bumps ubuntu from `99c3519` to `278628f`.

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

images/toolbox/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM ubuntu:24.04@sha256:99c35190e22d294cdace2783ac55effc69d32896daaa265f0bbedbcde4fbe3e5
+FROM ubuntu:24.04@sha256:278628f08d4979fb9af9ead44277dbc9c92c2465922310916ad0c46ec9999295
 
 LABEL maintainer="Antrea <projectantrea-dev@googlegroups.com>"
 LABEL description="A Docker image with useful tools (for networking) based on Ubuntu"