Add missing 'registration' property to 'relyingparty'

Author: danilopiazza

docs/modules/ROOT/pages/servlet/saml2/login/authentication-requests.adoc

@@ -143,10 +143,11 @@ spring:
   security:
     saml2:
       relyingparty:
-        okta:
-          assertingparty:
-            entity-id: ...
-            singlesignon.sign-request: false
+        registration:
+          okta:
+            assertingparty:
+              entity-id: ...
+              singlesignon.sign-request: false
 ----
 
 Java::

docs/modules/ROOT/pages/servlet/saml2/login/overview.adoc

@@ -886,16 +886,17 @@ spring:
   security:
     saml2:
       relyingparty:
-        okta:
-          signing.credentials: &relying-party-credentials
-            - private-key-location: classpath:rp.key
-              certificate-location: classpath:rp.crt
-          assertingparty:
-            entity-id: ...
-        azure:
-          signing.credentials: *relying-party-credentials
-          assertingparty:
-            entity-id: ...
+        registration:
+          okta:
+            signing.credentials: &relying-party-credentials
+              - private-key-location: classpath:rp.key
+                certificate-location: classpath:rp.crt
+            assertingparty:
+              entity-id: ...
+          azure:
+            signing.credentials: *relying-party-credentials
+            assertingparty:
+              entity-id: ...
 ----
 
 Second, in a database, you need not replicate the model of `RelyingPartyRegistration`.