Bump carthage-software/mago in /packages/default/notifier

Bumps [carthage-software/mago](https://github.com/carthage-software/mago) from 1.9.1 to 1.12.0.
- [Release notes](https://github.com/carthage-software/mago/releases)
- [Commits](carthage-software/mago@1.9.1...1.12.0)

---
updated-dependencies:
- dependency-name: carthage-software/mago
  dependency-version: 1.12.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

packages/default/notifier/composer.json

@@ -6,7 +6,7 @@
     },
     "require-dev": {
         "guzzlehttp/guzzle": "^7",
-        "carthage-software/mago": "1.9.1"
+        "carthage-software/mago": "1.12.0"
     },
     "config": {
         "allow-plugins": {