Fix some failures in autotest rendertest

Summary:
Revision 958c6336 to messageviewer/src/messagepartthemes
/default/templates/encryptedmessagepart.html made the "enc-simple" and
"enc-details" DIVs alternatives to each other, so they can't both appear
in the displayed result.  This patch removes enc-details from the expected
results.

Note: this eye-glazing patch does not fix all failures in rendertest.

enc-simple

enc-detail

Reviewers: dvratil

Reviewed By: dvratil

Subscribers: dvratil, kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D22959