Add missing optional-return note to tryIsp Javadoc

tryIsp returns Optional<IspResponse>, so its @return should note the
empty case like the other try* methods. The phrase had been misplaced
on the @param tag.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: oschwald

src/main/java/com/maxmind/geoip2/DatabaseProvider.java

@@ -209,7 +209,7 @@ IspResponse isp(InetAddress ipAddress) throws IOException,
      * Look up an IP address in a GeoIP ISP database.
      *
      * @param ipAddress IPv4 or IPv6 address to look up.
-     * @return an IspResponse for the requested IP address.
+     * @return an IspResponse for the requested IP address or empty if it is not in the DB.
      * @throws com.maxmind.geoip2.exception.GeoIp2Exception if there is an error looking up the IP
      * @throws java.io.IOException                          if there is an IO error
      */