Doc fix for `ClientConfiguration::getProxyUsername`
* this method returns the `http(s).proxyUser` system property,
not `http(s).proxyUsername`.
@@ -699,8 +699,8 @@ public class ClientConfiguration {
* object, or if not provided, checks the value of the Java system
* property for proxy user name according to {@link #getProtocol()}:
* i.e. if protocol is https, returns the value of the system
- * property https.proxyUsername, otherwise returns value of
- * http.proxyUsername.
+ * property https.proxyUser, otherwise returns value of
+ * http.proxyUser.
*
* @return The optional proxy user name the configured client will use if connecting through a
* proxy.
