Revert "Temporarily disable tst_QJSEngine tests [...]"

This reverts commit 17ae095602bf36ece892598e69f794ef982c603b.

The test can be re-enabled now.

Change-Id: I0134365edbfd4aed05665bf16b8e15221fe62d67
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Remove milliseconds before comparing JS + Qt date strings.

It seems that tst_qjsengine also needs:
https://codereview.qt-project.org/#change,65811

Change-Id: I5f5586f004dec047c3a1edebbc98d7ecde195bfd
Reviewed-by: John Layt <jlayt@kde.org>
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>