Make function declarations more portable in magic starter

hack/tfw_magic_start.sh

@@ -18,19 +18,19 @@ BACKEND_PORT="${BACKEND_PORT:-8888}"
 AVATAO_SECRET="${AVATAO_SECRET:-secret}"
 BUILD_CONTEXT="${BUILD_CONTEXT:-solvable}"
 
-function run_frontend()
+run_frontend()
 {
     cd $FRONTEND_PATH
     yarn start
 }
 
-function build_baseimage()
+build_baseimage()
 {
     cd $BASEIMAGE_PATH
     docker build -t $BASEIMAGE_NAME .
 }
 
-function run_backend()
+run_backend()
 {
     cd $BACKEND_PATH
     docker build -t $IMAGE_NAME -f ${BUILD_CONTEXT}/Dockerfile --build-arg BUILD_CONTEXT=$BUILD_CONTEXT --build-arg NOFRONTEND=1 .