Update build-clang-doxy.yml - switch back to main now confirmed same

Author: tyeth

.github/workflows/build-clang-doxy.yml

@@ -68,7 +68,6 @@ jobs:
         with:
           repository: adafruit/Wippersnapper_Boards
           path: ws-boards
-          ref: migrate-4mb-to-esptool
       - name: Install CI-Arduino
         run: bash ci/actions_install.sh
       - name: Install extra Arduino libraries