Fix rm(remove) chart issues

[TejaBeta]

Hello @hayorov 👋,
This PR will fix a current issue with rm functionality by using url from the index.yaml.

By doing so we can have two fixes,

1. WRT to bucketPath when used

helm gcs push app001-0.0.1.tgz my-bucket --bucketPath=app001

End result

gs://my-bucket
|---index.yaml
|     |--app001\
|     |    |--app001.0.0.1.tgz

but the rm kept trying to remove from gs://my-bucket/app001.0.0.1.tgz as the object doesn't exists in the path, it throws error.

2. Fixes this issue as well.

Thanks.