ci: use var instead of secret

[kanadgupta]

🧰 Changes

GitHub Actions now supports variables, so swapping out the version secret for a version variable.

Further reading: https://github.blog/changelog/2023-01-10-github-actions-support-for-configuration-variables-in-workflows/

🧬 QA & Testing

In the docs syncing dry run step, note how the version is no longer masked:

Here's what it looks like for the same workflow in main:

[erunion]

nice