Use single element in test

Author: tvernum

x-pack/plugin/identity-provider/src/test/java/org/elasticsearch/xpack/idp/saml/sp/SamlServiceProviderDocumentTests.java

@@ -147,9 +147,7 @@ private SamlServiceProviderDocument createFullDocument() throws GeneralSecurityE
         doc1.attributeNames.setEmail("urn:" + randomAlphaOfLengthBetween(4, 8) + "." + randomAlphaOfLengthBetween(4, 8));
         doc1.attributeNames.setName("urn:" + randomAlphaOfLengthBetween(4, 8) + "." + randomAlphaOfLengthBetween(4, 8));
         doc1.attributeNames.setRoles("urn:" + randomAlphaOfLengthBetween(4, 8) + "." + randomAlphaOfLengthBetween(4, 8));
-        doc1.attributeNames.setExtensions(
-            randomList(0, 3, () -> "urn:" + randomAlphaOfLengthBetween(4, 8) + "." + randomAlphaOfLengthBetween(4, 8))
-        );
+        doc1.attributeNames.setExtensions(List.of("urn:" + randomAlphaOfLengthBetween(4, 8) + "." + randomAlphaOfLengthBetween(4, 8)));
         return doc1;
     }