(maint) Fix branch name

While there is a redirect from master to main, better to use the
actual branch name, which is main.

Author: gep13

.github/workflows/label-sync.yml

@@ -21,7 +21,7 @@ jobs:
       - uses: EndBug/label-sync@v2
         with:
           config-file: |
-            https://raw.githubusercontent.com/chocolatey/.github/master/.github/labels.yml
+            https://raw.githubusercontent.com/chocolatey/.github/main/.github/labels.yml
             .github/labels.yml
           request-token: ${{ secrets.SYNC_TOKEN }} # Used when getting the config files.
           delete-other-labels: true # After initial run, and verification change this to true