Revert "fix(autotests): fix simpleWrite test in kwaylandbackendtest"

The commit message in wrong as the type must be test since this is a fix to
an autotest. And the scope autotest does not exist.

See https://cgit.kde.org/libkscreen.git/tree/CONTRIBUTING.md

The commit may be reapplied with correct header. See also
https://phabricator.kde.org/D27537#615130 for a suggestion.

This reverts commit 2fcd093919b88ebb619658a739f7f56e9134a82a.