remove anonymous gist dependency from benchmarks

[mollymerp]

per https://github.com/blog/2503-deprecation-notice-removing-anonymous-gist-creation

[jfirebaugh]

Alternatives:

• Create an oauth'd GitHub app that can gist on behalf of the user (cons: oauth is a pain, this will pollute folks' gist collections)
• Upload directly to S3 bucket (cons: requires access to AWS credentials)
• Find some other anonymous hosting service

[anandthakker]

Darn, just tried to fix this by generating a data URI that could be pasted into a PR, but GH markdown sanitizes that away (which makes sense)

[mourner]

There are no viable and easy alternatives, so we'll remove the share button for now -> #8066