After adding a warning for `{@link}` tags that refer to private/protected types, we see these warnings when building javadoc.

```
src/java.sql/share/classes/java/sql/DriverManager.java:62: warning: reference to non-visible type: ServiceLoader.load(Class, ClassLoader, Module) (use -protected or -private options to document non-public types)
 * via the {@linkplain ServiceLoader#load service-provider loading} mechanism.
           ^
```

It should instead point to