Update GitHub Actions workflow for Rush version sync

[nev21]

No description provided.

[Copilot]

Pull request overview

This PR updates the GitHub Actions workflow for syncing Rush version changes by switching from pull_request to pull_request_target trigger and configuring checkout actions to explicitly reference the PR head branch and repository. The bot identity is also updated to use the official Dependabot credentials.

Key Changes:

• Switched workflow trigger from pull_request to pull_request_target to enable write permissions
• Added explicit ref and repository parameters to checkout actions for accessing PR branch code
• Updated bot credentials from "dependabot-sync[bot]" to official "dependabot[bot]" identity

Files not reviewed (1)

• common/config/rush/npm-shrinkwrap.json: Language not supported

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (cf571b9) to head (1604130).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #285   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           26        26           
  Lines          458       458           
  Branches       113       113           
=========================================
  Hits           458       458           

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