Fix: Use valid Docker tag for SSHD service in test workflow

Updated .github/workflows/test.yml to use `rastasheep/ubuntu-sshd:jammy`
instead of `rastasheep/ubuntu-sshd:22.04`, as the latter tag was not found.
'jammy' corresponds to Ubuntu 22.04 and should resolve the Docker pull error
for the test service container.

Author: google-labs-jules[bot]

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     services:
       sshd:
-        image: rastasheep/ubuntu-sshd:22.04 # Pinned version
+        image: rastasheep/ubuntu-sshd:jammy # Updated to jammy for Ubuntu 22.04
         ports:
           - 2222:22
         # We will configure the sshd service using a step below