Improve with List.copyOf

The implementation code in SSLParameters could be improved with List.copyOf() method.

- return Collections.<SNIServerName>unmodifiableList(new ArrayList<>(sniNames.values()));
+ return List.copyOf(sniNames.values());

- return Collections.<SNIMatcher>unmodifiableList(new ArrayList<>(sniMatchers.values()));
+ return List.copyOf(sniMatchers.values());