doc: remove os.uptime() Windows note

The libuv 1.20.2 update in Node 10 aligned the Windows behavior
of os.uptime() with that of other operating systems. The return
value no longer contains a fraction component.

Refs: https://github.com/nodejs/node/pull/20129

PR-URL: https://github.com/nodejs/node/pull/20308
Refs: https://github.com/nodejs/node/pull/20129


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>