Fix slack notification action

[UrazAkgultan]

Description

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Checklist

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• Release Note: I have added a release note in the Mendix Docs repository relevant to the changes introduced in this PR.
  • Link to release note: [Provide the link here]
• Breaking Changes: This PR introduces breaking changes (e.g., changes that require updates to existing configurations, dependencies).
  • If yes, I have documented these breaking changes and provided guidance for users to adapt.
  • Details about breaking changes: [Provide details here, if applicable]

This PR contains

• Bug fix
• Feature
• Refactor
• Documentation
• Dependency Upgrade(s) (add versions)
• Other (describe)

Important Notes

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• Make sure the release note accurately describes the changes and impacts introduced by this PR.
• If documentation update is not required, add a comment with skip-docs-check to skip the docs check.

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What should be covered while testing?

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[UrazAkgultan]

skip-docs-check