Improve description of the icon setting

doc/administration/auth/oidc.md

@@ -34,7 +34,7 @@ The OpenID Connect will provide you with a client details and secret for you to
    gitlab_rails['omniauth_providers'] = [
      { 'name' => 'openid_connect',
        'label' => '<your_oidc_label>',
-       'icon' => '<url_to_custom_provider_icon>',
+       'icon' => '<custom_provider_icon>',
        'args' => {
          'name' => 'openid_connect',
          'scope' => ['openid','profile'],
@@ -59,7 +59,7 @@ The OpenID Connect will provide you with a client details and secret for you to
    ```yaml
      - { name: 'openid_connect',
          label: '<your_oidc_label>',
-         icon: '<url_to_custom_provider_icon>',
+         icon: '<custom_provider_icon>',
          args: {
            name: 'openid_connect',
            scope: ['openid','profile'],
@@ -84,8 +84,8 @@ The OpenID Connect will provide you with a client details and secret for you to
 
 1. For the configuration above, change the values for the provider to match your OpenID Connect client setup. Use the following as a guide:
    - `<your_oidc_label>` is the label that will be displayed on the login page.
-   - `<url_to_custom_provider_icon>` (optional) is the icon that will be displayed on the login page. Icons for the major social login platforms are built-in into GitLab,
-     but can be overridden by specifying this parameter.
+   - `<custom_provider_icon>` (optional) is the icon that will be displayed on the login page. Icons for the major social login platforms are built-in into GitLab,
+     but can be overridden by specifying this parameter. Both local paths and absolute URLs are accepted.
    - `<your_oidc_url>` (optional) is the URL that points to the OpenID Connect provider. For example, `https://example.com/auth/realms/your-realm`.
      If this value is not provided, the URL is constructed from the `client_options` in the following format: `<client_options.scheme>://<client_options.host>:<client_options.port>`.
    - If `discovery` is set to `true`, the OpenID Connect provider will try to auto discover the client options using `<your_oidc_url>/.well-known/openid-configuration`. Defaults to `false`.