Rename notebooks folder to templates

[alex-l-kong]

What is the purpose of this PR?

Closes #725. It's no longer necessary to suffix the templates folder with _ark; this is a remnant of when the toffy pipeline was here.

How did you implement your changes

Change any reference to templates_ark to templates.

[ngreenwald]

Looks good. Did you use an editor/github search to make sure you got all the old template_ark references? And did you try it out yourself with the new docker script to make sure it all works?

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[alex-l-kong]

@ngreenwald good catch, looks like Github search isn't reliable for Jupyter notebooks. Just one minor reference fix.

start_docker.sh works as expected, including with the -u flag.

[ngreenwald]

Sounds good. Going to wait to merge this in until we're ready for a new release to make sure people aren't stuck with an intermediate version