Update OIDC troubleshooting language

Signed-off-by: Vincent Fazio <vfazio@xes-inc.com>

doc/administration/auth/oidc.md

@@ -162,9 +162,9 @@ If you're having trouble, here are some tips:
    `https://accounts.google.com/.well-known/openid-configuration`.
 
 1. The OpenID Connect client uses HTTP Basic Authentication to send the
-   OAuth2 access token. For example, if you are seeing 401 errors upon
-   retrieving the `userinfo` endpoint, you may want to check your OpenID
-   Web server configuration. For example, for
+   OAuth2 access token if `client_auth_method` is not defined or if set to `basic`.
+   If you are seeing 401 errors upon retrieving the `userinfo` endpoint, you may
+   want to check your OpenID Web server configuration. For example, for
    [oauth2-server-php](https://github.com/bshaffer/oauth2-server-php), you
    may need to [add a configuration parameter to
    Apache](https://github.com/bshaffer/oauth2-server-php/issues/926#issuecomment-387502778).