README.md have a duplicate blog entry

[lbscorpio]

Summary

There are two below blogs on current README, but they are same content in fact. And the first URL can be updated to an official URL(https://www.ibm.com/cloud/blog/simplify-and-automate-deployments-using-gitops-with-ibm-multicloud-manager-3-1-2), the second URL already invalid.

Simplify and Automate Deployments Using GitOps with IBM Multicloud Manager 3.1.2:
https://medium.com/ibm-cloud/simplify-and-automate-deployments-using-gitops-with-ibm-multicloud-manager-3-1-2-4395af317359

Simplify and Automate Deployments Using GitOps with IBM Multicloud Manager:
https://www.ibm.com/blogs/bluemix/2019/02/simplify-and-automate-deployments-using-gitops-with-ibm-multicloud-manager-3-1-2/

Motivation

Documentation update

Proposal

By updating https://github.com/argoproj/argo-cd/blob/master/README.md

[lbscorpio]

I have raised PR 6246 for this issue, fyi, thanks.