fix(docs): Match user token update and prioritize internal integrations

[schew2381]

Background

As part of the change to Introduce Scope Hierarchy, I edited the page where you create user auth tokens to use the same dropdowns as internal integrations in getsentry/sentry#54651. You can test this for yourself here.

Changes

1. Clarify that user auth tokens are not editable after they are created. In order to change the scopes on them, you must create a new token.
2. Replace old picture of the create user auth page from box selectors to the new dropdowns
3. I moved user auth tokens to below integration tokens to hopefully have people favor integration > user tokens. In the future, we will probably look into eventually deprecating user auth tokens in favor of the other 2 tokens.
4. For the internal integration, I changed the wording from
   See our docs on Internal Integrations to learn more.
   to
   To get started, see our docs on Internal Integrations
   because it wasn't immediately clear to me which link in that section leads to the steps to create the integration.

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Name	Status	Preview	Comments	Updated (UTC)
sentry-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 21, 2023 10:42pm

[shanamatthews]

lgtm!