Fix quoting in GPG command for secrets archive

Author: adamtheturtle

docs/source/ci-setup.rst

@@ -36,7 +36,7 @@ Add the encrypted secrets files to the repository:
 .. code-block:: console
 
    $ tar cvf secrets.tar ci_secrets/
-   $ gpg --yes --batch --passphrase=${PASSPHRASE_FOR_VUFORIA_SECRETS} --symmetric --cipher-algo AES256 secrets.tar
+   $ gpg --yes --batch --passphrase="${PASSPHRASE_FOR_VUFORIA_SECRETS}" --symmetric --cipher-algo AES256 secrets.tar
    $ git add secrets.tar.gpg
    $ git commit -m "Update secret archive"
    $ git push