Drop mention of non-working 'url' config option.

Since the functional description is that it would fill OrganizationURL,
for which a config option already exists, there's no use to make it
work, rather just simplify and drop the docs.

modules/saml/docs/sp.md

@@ -390,16 +390,6 @@ Options
 `SingleLogoutServiceLocation`
 :   The Single Logout Service URL published in the generated metadata.
 
-`url`
-:   A URL to your service provider. Will be added as an OrganizationURL-element in the metadata.
-
-:   This option can be translated into multiple languages by specifying the value as an array of language-code to language-specific URL:
-
-        'url' => [
-            'en' => 'http://sp.example.net/en/info.html',
-            'no' => 'http://sp.example.net/no/info.html',
-        ],
-
 `validate.logout`
 :   Whether we require signatures on logout messages sent to this SP.