security: remove debug step that could expose GITHUB_TOKEN

Removed the "Debug Git Config" step from all workflows as it could
potentially expose the GITHUB_TOKEN in logs (shown in git URL rewrites).

Now that the workflows are passing with the HTTPS libsignal fix,
this debug output is no longer needed.

Addresses security concern raised by Copilot AI in PR #170.

https://claude.ai/code/session_015R3U3kiprQiNTTNNt31Sg6

.github/workflows/build.yml

@@ -44,13 +44,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-yarn-
 
-      - name: Debug Git Config
-        run: |
-          echo "=== Git URL Rewrites ==="
-          git config --global --get-regexp url
-          echo "=== Environment ==="
-          env | grep -i git || true
-
       - name: Install dependencies
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}