doc: fix CCM cipher example in MJS

The original example used 'return' to terminate the current control
flow, which is valid in CommonJS. When the example was copied and
modified to use MJS syntax, the 'return' statement was left in but is
not allowed.

Refs: https://github.com/nodejs/node/pull/37594

PR-URL: https://github.com/nodejs/node/pull/39949


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>