OIDC provider: hide "Choosing where to go" splash when authorizing an application

[candlerb]

Is your feature request related to a problem? Please describe.
This is only a minor annoyance.

Since moving to Vault 1.12.2, when an application is is in the middle of authenticating against the Vault OIDC provider, a set of menu options is now displayed on the right hand side:

This is only visible to the user briefly, while Vault is authenticating the user and before they are redirected back to the callback endpoint - usually only a second or so. But it does give some uncertainty as to whether the user is supposed to have selected one of these options.

Describe the solution you'd like
Hide this sidebar in the authorization endpoint (or indeed, for anything other than the home page)

Describe alternatives you've considered
In this case, Vault could display something more useful like "Authorizing..."

Explain any additional use-cases
N/A

Additional context
Previous version of Vault was 1.11.3, although I'm not 100% sure it was the most recent upgrade which caused this to start happening. The one before was 1.10.1.