Fix failing autotest grantleeheaderstyletest

Summary:
defaultgrantleeheaderstyleplugin/theme/5.2/header.html originally produced
a chunk of HTML with two unclosed DIVs, and this test added two closing
tags in order to validate it. Revision a19720ae8e0a changed header.html
to have just one unclosed DIV.

This patch adapts the test to the change in header.html, and cleans up
some other minor bitrot.

Subscribers: kde-pim

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D22892