Update intro to OIDC SL1 to clarify intent

[dhs-BI]

Following the discussion on the May 6, 2025 call, the intro to the OIDC SL1 profile needs to be updated to clarify the intent of the profile is not to provide generic API access, only for federated login and access to the userinfo endpoint. This absolves IPSIE OIDC SL1 of the need for DPoP and refresh tokens as discussed in #69.

[dhs-BI]

I'll try to write this up in the next week or so.

[deansaxe]

Apologies, this was not yet completed. Queuing this up for resolution soon.

[deansaxe]

See the PR at openid/ipsie-openid-sl1#3.

[deansaxe]

Further updates made to the PR based on feedback from @gffletch. Queued for review on July 1, 2025.

[deansaxe]

Reviewed again by the WG and merged by @aaronpk. Closing this issue.