fs: use IsSafeJsInt instead of IsNumber for ftruncate

PR-URL: https://github.com/nodejs/node/pull/26572


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>