This commit:
* Removes the unnecessary screenshot.
* Reorders the instructions and combines them in to 4 steps.
* Improves the contents of the webhook-url-with-bot-email-indented.md
macro and makes it more consistent with create-bot-construct-url.md.
* Sets the recommended stream name to "commits", since that's what
the webhook function for Beanstalk expects in
zerver/webhooks/beanstalk/view.py. This allows us to use the
create-stream.md macro.