Steam Flatpak no longer starts via launcher

#### Your system information

* Steam Version: 1721173382
* Steam Client Build Date: Wed, Jul 17 1:22 AM UTC -08:00
* Steam Web Build Date: Mon, Jun 24 9:16 PM UTC -08:00
* Steam API Version: SteamClient021
* Distribution (e.g. Ubuntu): Ubuntu 22.04
* Opted into Steam client beta?: No
* Have you checked for system updates?: Yes
* GPU: AMD dGPU on Desktop | AMD iGPU on laptop

#### Please describe your issue in as much detail as possible:

Up until a few days ago, clicking on the steam launcher on ubuntu's dock launched steam. Now nothing happens. I can still open it via the command line with `flatpak run com.valvesoftware.Steam`

Reproduce the failure by clicking the Ubuntu dock launcher, then compare it with `flatpak run com.valvesoftware.Steam`, which still starts Steam. No file, test, or entry point is identified in the report; done means restoring launcher startup while preserving the working command-line launch.

Written by the indexing model from the issue text.