fix tests

Author: richard-dennehy

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/jwt/JwtRealmSettingsTests.java

@@ -606,7 +606,7 @@ public void testInvalidProxySchemeThrowsError() {
 
         assertThat(
             e.getMessage(),
-            equalTo(Strings.format("Invalid value [https] for [%s]. Allowed values are [http].", proxySchemeSettingKey))
+            equalTo(Strings.format("Invalid value [%s] for [%s]. Allowed values are [http].", scheme, proxySchemeSettingKey))
         );
     }