Use workflow GitHub token as default `GITHUB_TOKEN`

[KeisukeYamashita]

Description

I have configured default token ${{ github.token }} so that users doesn't need to specify the ${{ secrets.GITHUB_TOKEN }} every time.

Motivation and Context

Like in the README.md's example, when we want to use this workflow, we need to at least specify the workflow run's token ${{ secrets.GITHUB_TOKEN }} or any custom tokens. But, on workflow run's token, we can use the default value and remove the GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] Enhancement (changes that improvement of current feature or performance)
• [x] Refactoring (changes that neither fixes a bug nor adds a feature)
• [ ] Test Case (changes that add missing tests or correct existing tests)
• [ ] Code style optimization (changes that do not affect the meaning of the code)
• [ ] Docs (changes that only update documentation)
• [ ] Chore (changes that don't modify src or test files)

Self Check before Merge

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[KeisukeYamashita]

@bubkoo Hi, thank you for your nice work. Because there were no code owners, the default reviewers are not assigned. Thus, I have mentioned you 🙏 PTAL when you got a chance!

Thank you in advance.