Update environment variable for Copilot CLI

Replaced GH_TOKEN with GITHUB_TOKEN for Copilot CLI.

Author: raykao

.github/workflows/copilot.generate-docs.yml

@@ -20,16 +20,14 @@ jobs:
           fetch-depth: 0
 
       - name: Install GitHub Copilot CLI
-        env:
-          GH_TOKEN: ${{ secrets.COPILOT_CLI_TOKEN }}
         run: |
           curl -fsSL https://gh.io/copilot-install | bash
           echo "Installed Copilot CLI version:"
           copilot --version
                     
       - name: Analyze and delegate to Copilot
         env:
-          GH_TOKEN: ${{ secrets.COPILOT_CLI_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.COPILOT_CLI_TOKEN }}
         run: |
           echo "Analyzing commit ${{ github.sha }}"
           echo "Loading documentation criteria from prompt..."