Documentation of default for file_chunk_count is incorrect.

In 7.13 the documentation for the file_chunk_count states "Default value is 4611686018427387903". This is not true. The [default](https://github.com/logstash-plugins/logstash-input-file/blob/9be8dc26356c40050a06b074acf33d009fecf90e/lib/filewatch/bootstrap.rb#L14) is 4611686018427387903/32768. That is, 140737488355327. Also this assumes a 64-bit JVM.