chore(deps): Bump blinklabs-io/mithril-signer

Bumps [blinklabs-io/mithril-signer](https://github.com/blinklabs-io/docker-mithril-signer) from 0.2.221-1 to 0.2.228-1.
- [Release notes](https://github.com/blinklabs-io/docker-mithril-signer/releases)
- [Commits](blinklabs-io/docker-mithril-signer@v0.2.221-1...v0.2.228-1)

---
updated-dependencies:
- dependency-name: blinklabs-io/mithril-signer
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Dockerfile

@@ -23,7 +23,7 @@ RUN echo "Building tags/${NODE_VERSION}..." \
 FROM ghcr.io/blinklabs-io/cardano-cli:10.4.0.0-1 AS cardano-cli
 FROM ghcr.io/blinklabs-io/cardano-configs:20250213-1 AS cardano-configs
 FROM ghcr.io/blinklabs-io/mithril-client:0.10.5-1 AS mithril-client
-FROM ghcr.io/blinklabs-io/mithril-signer:0.2.221-1 AS mithril-signer
+FROM ghcr.io/blinklabs-io/mithril-signer:0.2.228-1 AS mithril-signer
 FROM ghcr.io/blinklabs-io/nview:0.10.6 AS nview
 FROM ghcr.io/blinklabs-io/txtop:0.12.2 AS txtop