Bump kamal from 2.5.3 to 2.6.0

Bumps [kamal](https://github.com/basecamp/kamal) from 2.5.3 to 2.6.0.
- [Release notes](https://github.com/basecamp/kamal/releases)
- [Commits](https://github.com/basecamp/kamal/compare/v2.5.3...v2.6.0)

---
updated-dependencies:
- dependency-name: kamal
  dependency-version: 2.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -127,13 +127,13 @@ GEM
       actionview (>= 5.0.0)
       activesupport (>= 5.0.0)
     json (2.11.3)
-    kamal (2.5.3)
+    kamal (2.6.0)
       activesupport (>= 7.0)
       base64 (~> 0.2)
       bcrypt_pbkdf (~> 1.0)
       concurrent-ruby (~> 1.2)
       dotenv (~> 3.1)
-      ed25519 (~> 1.2)
+      ed25519 (~> 1.4)
       net-ssh (~> 7.3)
       sshkit (>= 1.23.0, < 2.0)
       thor (~> 1.3)