fix: Trigger workflow 4 before closing

[chriswblake]

This pull request includes several changes to the GitHub workflow and documentation for a Copilot exercise. The most important changes involve updating the workflow triggers, modifying the order of instructions in the exercise, and adjusting the conditions for job execution.

Updates to workflow triggers and job conditions:

• .github/workflows/4-copilot-on-github.yml: Changed the pull_request event types to [edited] and added a new pull_request_review event type with [submitted] to trigger the workflow.
• .github/workflows/4-copilot-on-github.yml: Removed the condition that checks if the pull request is merged for the find_exercise job.

Modifications to exercise instructions:

• .github/steps/4-copilot-on-github.md: Reordered the instructions to wait for Mona's feedback before merging the pull request, and corrected a grammatical error.

Simplification of job steps:

• .github/workflows/4-copilot-on-github.yml: Removed the --edit-last flag from the gh issue comment command in the step that updates the comment for the final review.