Update the event's registration team's README.md

[reylejano]

This PR updates the Registration Team handbook:

• removes the 2 paths of the registration form (new and active contributor), we no longer do a new contributor path
• updates the approval process, updates the commands to generate the org members list to include etcd, gives an alternate command to generate the list
• add new sections for exceptions, dietary requirements, and celebration guests
• removed content about two tracks: Active Contributor and New Contributor Track. We no longer have two tracks

[k8s-ci-robot]

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[reylejano]

/assign @salaxander @ameukam /cc @mfahlandt @stmcginnis @savitharaghunathan @tokt

[stmcginnis]

/lgtm

Would be good to have the non-org member section figured out, but this at least gives us a good placeholder to know that it is something that might require a little more discussion.

[tokt]

/lgtm

Thank you so much!!

[salaxander]

One small non-blocking nit

/lgtm

[stmcginnis]

Good catch!

/lgtm

[ameukam]

/lgtm cc @jberkus @mrbobbytables

[k8s-ci-robot]

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