Grammar tweak

Signed-off-by: yuxiaobo <yuxiaobogo@163.com>

docs/chart_repository_sync_example.md

@@ -38,7 +38,7 @@ Building synchronization state...
 Starting synchronization
 Would copy file://fantastic-charts/alpine-0.1.0.tgz to gs://fantastic-charts/alpine-0.1.0.tgz
 Would copy file://fantastic-charts/index.yaml to gs://fantastic-charts/index.yaml
-Are you sure you would like to continue with these changes?? [y/N]} y
+Are you sure you would like to continue with these changes? [y/N]} y
 Building synchronization state...
 Starting synchronization
 Copying file://fantastic-charts/alpine-0.1.0.tgz [Content-Type=application/x-tar]...