update authelia example to authelia v4.38

[hendrik1120]

Hello, this small PR will update the authelia example configuration to the latest authelia version.

Authelia v4.38 will default to using the client_secret_basic authentication method, as described in the release post to follow the OIDC specification.

Not setting the token_endpoint_auth_method to client_secret_post will generate the following error:

Access Request failed with error: Client authentication failed (e.g., unknown client, no client authentication included, or unsupported authentication method). 
The request was determined to be using 'token_endpoint_client_auth_method' method 'client_secret_post', however the OAuth 2.0 client does not support this method. 
The registered client with id 'jellyfin' only supports 'token_endpoint_client_auth_method' method 'client_secret_basic'.

Please note that this configuration change is not backwards compatible to any version prior to v4.38.

I am open to any feedback regarding this change. If you don't experience the same issue while using authelia v4.38 please leave a comment down below.

[9p4]

Perhaps the docs should include a note for both versions instead of replacing it outright? ie: "for Authelia < 4.38: ..., and for Authelia >= 4.38: ..." or something of the sort.

[hendrik1120]

From my point of view, there was no reason to stick to an old minor release without any security updates while OIDC still being in beta, but I added the old config back.

[james-d-elliott]

Thanks for this! We're also adding a guide to our site for reference. Would really appreciate a sanity check on it as I don't use Jellyfin (particularly around the steps involved in configuring the plugin/jellyfin itself):

https://deploy-preview-7148--authelia-staging.netlify.app/integration/openid-connect/jellyfin/