Some systems default to a nofile ulimit of 65535. To reduce the pain of
deploying Elasticsearch to such systems, this commit lowers the required
limit from 65536 to 65535.
On Windows the JDK uses `CreateFileW` which has a stupidly high
limit for the number of `Handle`s it can make - `16 * 1024 * 1024`.
So this isn't really a problem on Windows at all.
Closes#20732