Update Okta instructions

I recently verified that the comments in
are applicable and resolve the errors that will occur if the current
instructions are followed.

The serviceProviderEntityId setting described in the issue does not
appear to be required.

Change-Id: Iea252cfccab505a87b76185c00e3acdd47cdc4ec
diff --git a/okta/README.md b/okta/README.md
index 4d67ba9..45bf0e5 100644
--- a/okta/README.md
+++ b/okta/README.md
@@ -2,7 +2,7 @@
 - Create a new SAML 2.0 application.
 - Set the following parameters:
-  - Single sign on URL: http://gerrit.site.com/plugins/saml/callback
+  - Single sign on URL: http://gerrit.site.com/plugins/saml/callback?client_name=SAML2Client
   - Check "Use this for Recipient URL and Destination URL".
   - Audience URI (SP Entity Id): http://gerrit.site.com/plugins/saml/callback
   - We need to set up the attributes in the assertion to send the right
@@ -17,4 +17,4 @@
       do not do so, the name will be taken from the NameId provided by
       the assertion.  This is why in Okta we set the application username to
       "Okta username prefix".
-- Obtain your IdP metadata (either URL or a local XML file)
\ No newline at end of file
+- Obtain your IdP metadata (either URL or a local XML file)