Remove Banzai Cloud

[danderson]

Related issue: #2172

• Company was acquired by Cisco in 2020
• All activity on github and related CNCF spaces stopped >1 year ago, aside from automated depaware updates.
• All three domains (banzai.cloud, app.banzaicloud.io, backyards.banzaicloud.io) are hard down at the DNS level. All domains are delegated to AWS Route53, which is responding REFUSED - indicating Route53 is no longer configured to serve those domains. My guess is the AWS account was shut down.
• Another open source project removed references to banzai cloud around a year ago, due to the link becoming dead at that time.
• A final piece of hosting for Banzai's products went down 2 weeks ago, there has been no response at all to repeated requests for help from its users.
• I failed to find any way to contact banzai that doesn't go through one of the dead DNS zones.

This all paints a picture of Cisco winding up the infrastructure of one of their acquisitions, and the former employees of banzai now working on something else.