doc: add and unify return statements in crypto.md

Conform return statements to the style guide and tool parsers.

Also bring back a description fragment
that seems to be erroneously deleted in
nodejs@1e07acd

PR-URL: nodejs#19853
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

doc/api/crypto.md

@@ -1673,9 +1673,8 @@ console.log(aliceSecret === bobSecret);
 <!-- YAML
 added: REPLACEME
 -->
-
-Returns `true` if and only if a FIPS compliant crypto provider is
-currently in use.
+- Returns: {boolean} `true` if and only if a FIPS compliant crypto provider is
+  currently in use.
 
 ### crypto.getHashes()
 <!-- YAML