coin: always use the latest platforms for CI build

Change the CI dependencies so that we always get the VM configurations
from the qt5.git dev branch. This makes sure that all Yocto builds,
regardless of the Qt version, are using the same host VM version.

Pick-to: 6.5 6.4 6.2
Change-Id: Iceb5ca006b8d83ed636d59566a115d64d3919e38
Reviewed-by: Mikko Gronoff <mikko.gronoff@qt.io>

coin/dependencies.yaml

@@ -1,2 +1,5 @@
+product_dependency:
+  ../../qt/qt5:
+      ref: "dev"
 dependencies:
   {}