fix(builder): Fixed invalid redirect syntax

Author: johanneswuerbach

builder/image/slugbuilder/builder/install-buildpacks

@@ -9,9 +9,10 @@ download_buildpack() {
     buildpack_commit="$2"
 
     git clone $buildpack_url $BUILDPACK_INSTALL_PATH/$buildpack_name
-    pushd $BUILDPACK_INSTALL_PATH/$buildpack_name 2>&1 >/dev/null
+    pushd $BUILDPACK_INSTALL_PATH/$buildpack_name &>/dev/null
         git checkout --quiet $buildpack_commit
-    popd 2>&1 >/dev/null
+    popd &>/dev/null
+
 }
 
 mkdir -p $BUILDPACK_INSTALL_PATH