Fix a typo

manage.sh

@@ -6,7 +6,7 @@ fetch() {
     git clone $FRONTEND_REPO --branch $BRANCH --depth 1 .tmp/fe
     git clone $BACKEND_REPO --branch $BRANCH --depth 1 .tmp/be
     FRONTEND_REPO=.tmp/fe
-    BACKEND_REPO=.tmp/fe
+    BACKEND_REPO=.tmp/be
   fi
   rm -rf docs/frontend
   rm -rf docs/backend