Update Client Secret instructions in oidc.md

Clarify instructions for adding the Client Secret based on authentication method.

Author: Karuna-Mendix

content/en/docs/marketplace/platform-supported-content/modules/oidc.md

@@ -350,7 +350,7 @@ In this case, the OIDC client is the app you are making.
 
     {{% alert color="info" %}}After a key renewal, some SSO requests may fail if your IdP does not immediately refresh its key cache. {{% /alert %}}
 
-5. Add the **Client Secret**.
+5. Add the **Client Secret** if you choose `client_secret_basic` or `client_secret_post` as client authentication method.
 6. If you have the **Automatic Configuration URL** (also known as the *well-known endpoint*), enter it and click **Import Configuration** to automatically fill the other endpoints.
 
     {{% alert color="info" %}} If the endpoint URL does not already end with `/.well-known/openid-configuration`, include it at the end. According to the specifications, the URL you need to enter typically ends with `/.well-known/openid-configuration`. {{% /alert %}}