Update redirect_uri list for OIDC Sinatra dev app

[monfresh]

Why: To be able to test SP-initiated logout locally

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[jmhooper]

Is this depending on prefix matching, or is the root the logout url?

[jmhooper]

I think it is fine either way, I'm just curious

[monfresh]

From what I can tell, it's set to the root: https://github.com/18F/identity-oidc-sinatra/blob/master/app.rb#L127

https://github.com/18F/identity-oidc-sinatra/blob/master/.env.example#L8

[jmhooper]

Hm, that's definitely interesting