Clarify property docs. Fixes #1264

spring-cloud-context/src/main/java/org/springframework/cloud/bootstrap/config/PropertySourceBootstrapProperties.java

@@ -42,7 +42,8 @@ public class PropertySourceBootstrapProperties {
 	/**
 	 * Flag to indicate that when {@link #setAllowOverride(boolean) allowOverride} is
 	 * true, external properties should take lowest priority and should not override any
-	 * existing property sources (including local config files). Default false.
+	 * existing property sources (including local config files). Default false. This will
+	 * only have an effect when using config first bootstrap.
 	 */
 	private boolean overrideNone = false;