fix(ci): remove duplicate submodule sync code in docker-build-push

The Sync submodule locally step had an identical duplicate block: after
cd-ing into SUBNODULE_PATH in the first block, the second block tried
cd SUBNODULE_PATH again, causing 'No such file or directory' since
the working directory was already inside the submodule path.

Also added cd $GITHUB_WORKSPACE at the end of the first block to
ensure the next step starts from the workspace root.

.github/workflows/docker-build-push.yml

@@ -201,11 +201,7 @@ jobs:
             cd "$SUBMODULE_PATH"
             git fetch origin "$DISPATCH_SHA"
             git checkout "$DISPATCH_SHA"
-          fi
-          if [ "$EVENT_NAME" = "repository_dispatch" ] && [ -n "${DISPATCH_SHA:-}" ]; then
-            cd "$SUBMODULE_PATH"
-            git fetch origin "$DISPATCH_SHA"
-            git checkout "$DISPATCH_SHA"
+            cd "${GITHUB_WORKSPACE}"
           fi
 
       - uses: docker/login-action@v4