doc: fix return type of `crypto.getFips()`

`crypto.getFips()` returns a number, not a boolean.

PR-URL: https://github.com/nodejs/node/pull/32580


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Signed-off-by: Richard Lau <riclau@uk.ibm.com>