postEdit needs to run before GS logging

The ext.gettingstarted.logging module didn't depend on postEdit as
taskToolbar does; I think that's why openTask sometimes logs
page-impression instead of page-save-success.

Bug: 50204
Change-Id: I55b6a70d9318fef104e383e7aba6931bbfbf840b
Merge "postEdit needs to run before GS logging"