docs: faq: specify "using inline shell scripts"

(cherry picked from commit 3faafb1dee59093b03ee3e84860094d4b1e069b5)

docs/faq.rst

@@ -132,6 +132,7 @@ key file based encryption with a blank passphrase. See
 .. _password_env:
 .. note:: Be careful how you set the environment; using the ``env``
           command, a ``system()`` call or using inline shell scripts
+          (e.g. ``BORG_PASSPHRASE=hunter12 borg ...``)
           might expose the credentials in the process list directly
           and they will be readable to all users on a system. Using
           ``export`` in a shell script file should be safe, however, as