chore(deps): update ubuntu:22.04 docker digest to 590f59c (#233)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

discourse_rock/rockcraft.yaml

@@ -5,7 +5,7 @@ name: discourse
 summary: Discourse rock
 description: Discourse OCI image for the Discourse charm
 base: [email protected]
-# renovate: base: ubuntu:22.04@sha256:1b8d8ff4777f36f19bfe73ee4df61e3a0b789caeff29caa019539ec7c9a57f95
+# renovate: base: ubuntu:22.04@sha256:590f59cd1a88bebe6293510a76b28a92a28782f483a1ec1f69ccbc716735b796
 run-user: _daemon_  # UID/GID 584792
 license: Apache-2.0
 version: "1.0"