Revert "Temporarily pin qtbase to a working version..."

This reverts commit 57c81a2b4b67bc001a28060527325f4016e42ffb

qtbase should be fixed now

Change-Id: I8179509d7549955ee9f78b3213f59c3a1f5e5c59
Reviewed-by: Lars Knoll <lars.knoll@digia.com>