not_authed error when the pr is opened by dependabot

Hello,

I've set up a workflow that uses your action to send notification to our slack channels.

The action works very well on all pr's except when is opened by github dependabot, for some reason it fails always, here's the log

2021-08-08T22:03:39.7832279Z Found online and idle hosted runner(s) in the current repository's organization account that matches the required labels: 'ubuntu-latest'
2021-08-08T22:03:39.7832335Z Waiting for a hosted runner in 'organization' to pick this job...
2021-08-08T22:03:47.1028911Z Current runner version: '2.279.0'
2021-08-08T22:03:47.1053659Z ##[group]Operating System
2021-08-08T22:03:47.1054490Z Ubuntu
2021-08-08T22:03:47.1054938Z 20.04.2
2021-08-08T22:03:47.1055327Z LTS
2021-08-08T22:03:47.1055796Z ##[endgroup]
2021-08-08T22:03:47.1056343Z ##[group]Virtual Environment
2021-08-08T22:03:47.1056985Z Environment: ubuntu-20.04
2021-08-08T22:03:47.1057488Z Version: 20210803.0
2021-08-08T22:03:47.1058497Z Included Software: https://github.com/actions/virtual-environments/blob/ubuntu20/20210803.0/images/linux/Ubuntu2004-README.md
2021-08-08T22:03:47.1059809Z Image Release: https://github.com/actions/virtual-environments/releases/tag/ubuntu20%2F20210803.0
2021-08-08T22:03:47.1060644Z ##[endgroup]
2021-08-08T22:03:47.1062431Z ##[group]GITHUB_TOKEN Permissions
2021-08-08T22:03:47.1063663Z Actions: read
2021-08-08T22:03:47.1064301Z Checks: read
2021-08-08T22:03:47.1064841Z Contents: read
2021-08-08T22:03:47.1065322Z Deployments: read
2021-08-08T22:03:47.1065942Z Discussions: read
2021-08-08T22:03:47.1066472Z Issues: read
2021-08-08T22:03:47.1066980Z Metadata: read
2021-08-08T22:03:47.1067458Z Packages: read
2021-08-08T22:03:47.1067994Z PullRequests: read
2021-08-08T22:03:47.1068559Z RepositoryProjects: read
2021-08-08T22:03:47.1069181Z SecurityEvents: read
2021-08-08T22:03:47.1069674Z Statuses: read
2021-08-08T22:03:47.1070325Z ##[endgroup]
2021-08-08T22:03:47.1073249Z Prepare workflow directory
2021-08-08T22:03:47.1658502Z Prepare all required actions
2021-08-08T22:03:47.1668276Z Getting action download info
2021-08-08T22:03:47.5570558Z Download action repository 'voxmedia/github-action-slack-notify-build@v1.5.0'
2021-08-08T22:03:49.2057247Z Download action repository 'actions/setup-java@v1'
2021-08-08T22:03:49.3454178Z Download action repository 'aws-actions/configure-aws-credentials@v1'
2021-08-08T22:03:49.5251301Z Download action repository 'actions/checkout@v2'
2021-08-08T22:03:49.6841035Z Download action repository 'mikepenz/action-junit-report@v2.0.3'
2021-08-08T22:03:49.9751443Z ##[group]Run voxmedia/github-action-slack-notify-build@v1.5.0
2021-08-08T22:03:49.9752206Z with:
2021-08-08T22:03:49.9752608Z   channel: tech-bit-testing
2021-08-08T22:03:49.9753026Z   status: STARTING
2021-08-08T22:03:49.9753384Z   color: warning
2021-08-08T22:03:49.9753694Z env:
2021-08-08T22:03:49.9754283Z   SLACK_BOT_TOKEN: 
2021-08-08T22:03:49.9754726Z ##[endgroup]
2021-08-08T22:03:50.7116938Z ##[error]Error: An API error occurred: not_authed
2021-08-08T22:03:50.7218265Z ##[group]Run voxmedia/github-action-slack-notify-build@v1.5.0
2021-08-08T22:03:50.7218914Z with:
2021-08-08T22:03:50.7219298Z   channel: tech-bit-testing
2021-08-08T22:03:50.7219720Z   status: FAILED
2021-08-08T22:03:50.7220053Z   color: danger
2021-08-08T22:03:50.7220379Z env:
2021-08-08T22:03:50.7220700Z   SLACK_BOT_TOKEN: 
2021-08-08T22:03:50.7221042Z ##[endgroup]
2021-08-08T22:03:50.8844021Z ##[error]Error: An API error occurred: not_authed
2021-08-08T22:03:50.8855933Z Cleaning up orphan processes

Thank you

voxmedia / github-action-slack-notify-build

not_authed error when the pr is opened by dependabot #57