Avoid persisting credentials on checkout step of the Github actions

[arash77]

Adding persist-credentials: false into the checkout step of the Github action workflows will prevent storing sensitive credentials for future jobs, which will increase the security of workflows.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[arash77]

This will cause GITHUB_TOKEN not to be accessible automatically anymore in the workflows and steps needing GitHub authentication (write access) must re-authenticate.