Bump slackapi/slack-github-action from 1.23.0 to 1.26.0

Bumps [slackapi/slack-github-action](https://github.com/slackapi/slack-github-action) from 1.23.0 to 1.26.0.
- [Release notes](https://github.com/slackapi/slack-github-action/releases)
- [Commits](slackapi/slack-github-action@v1.23.0...v1.26.0)

---
updated-dependencies:
- dependency-name: slackapi/slack-github-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/slack-notify.yml

@@ -11,7 +11,7 @@ jobs:
     steps:
       - name: Send message to Slack channel
         id: slack
-        uses: slackapi/slack-github-action@v1.23.0
+        uses: slackapi/slack-github-action@v1.26.0
         env:
           SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
           PROJECT_NAME: 'iOS CustomerIO SDK'