Update dogfood-policy-updater-latest-safari.sh

[allenhouchins]

This pull request simplifies and improves the automation for updating Safari version policies on macOS by switching from a multi-line YAML query to a single-line query and streamlining the associated update script. The changes make the update process more robust, easier to maintain, and less error-prone, especially when parsing and updating the policy file.

Policy and script simplification:

• Converted the query field in update-safari.yml from a multi-line YAML block to a single-line statement, reducing complexity and making it easier to update programmatically.

Script robustness and maintainability:

• Updated .github/scripts/dogfood-policy-updater-latest-safari.sh to extract and update the single-line query instead of handling a multi-line block, greatly simplifying the parsing and replacement logic. [1] [2]
• Improved error handling for environment variables, requiring only the essential DOGFOOD_AUTOMATION_TOKEN to be set, and clarified error messages.
• Enhanced validation of the Safari feed response by checking for valid JSON and explicit API errors using jq, making the update process more reliable.
• Changed the update workflow to write changes directly to the file and rely on GitHub Actions to create pull requests, removing the script's own git and PR logic for a cleaner CI/CD process.

[allenhouchins]

@lukeheath hoping this is the last time I need your review on this one! Workflows are difficult to test and I put myself on a bad path with having a poorly constructed query in my policy that this script is supposed to parse.