Update dependencies to platform version 1.28.0

[danielpeach]

Event

{
  "branchName": "release-1.28.x",
  "createTag": true,
  "dependencyUpdates": [
    {
      "depName": "echo",
      "depVersion": "2.34.2"
    },
    {
      "depName": "kork",
      "depVersion": "7.136.0"
    }
  ],
  "hasDependencyUpdates": true,
  "newGradleProperties": "spinnakerRelease=1.28.0\norg.gradle.parallel=true\n\nspinnakerGradleVersion=8.6.0\npf4jVersion=3.2.0\nkorkVersion=7.136.0\nechoVersion=2.34.2\nkotlinVersion=1.3.72",
  "orgName": "spinnaker-plugin-examples",
  "platformVersion": "1.28.0",
  "repoId": "MDEwOlJlcG9zaXRvcnkyNzYzODM1MTE=",
  "repoName": "notificationPlugin"
}