Restricted permission to main GitHub action

[naveensrinivasan]

• Restricted the permission for the main.yml GitHub action
• Define permissions for GitHub Actions #5726

Pull Request Checklist

• All changes are Go version 1.15 compliant
• Your PR passes all CI checks. If a check cannot be passed for a justifiable reason, that reason must be stated in the commit message and PR description.
• If this is your first time contributing, we recommend you read the Code Contribution Guidelines
  • The code being submitted is commented according to Code Documentation and Commenting
  • Commits have a logical structure according to Ideal Git Commit Structure
• For new code: Code is accompanied by tests which exercise both the positive and negative (error paths) conditions (if applicable)
• For bug fixes: If possible, code is accompanied by new tests which trigger the bug being fixed to prevent regressions
• Any new logging statements use an appropriate subsystem and logging level
• For code and documentation: lines are wrapped at 80 characters (the tab character should be counted as 8 characters, not 4, as some IDEs do per default)
• A description of your changes should be added to running the release notes for the milestone your change will land in.

[orijbot]

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