[Doc] Update Kubernetes Membership Scheme Installation steps

[sajinieKavindya]

Description:
In https://github.com/wso2/kubernetes-common/blob/master/kubernetes-membership-scheme/README.md#installation, it is mentioned that the kubernetes-membership-scheme-1.0.0.jar file should be copied to repository/components/dropins directory of the Carbon server.

But to configure Kubernetes scheme in EI 6.0.0 and upwards, kubernetes-membership-scheme-1.0.0.jar file should be copied to [EI_HOME]/dropins directory if it is an OSGI bundle. Otherwise, it should be copied to [EI_HOME]/lib directory.