Sector Six: missing shared library

**Game information**
Sector Six
https://store.steampowered.com/app/465020/Sector_Six/

**Distribution name and version where applicable**
Fedora release 34 (Thirty Four)

**Flatpak info**
`flatpak --version`
Flatpak 1.10.2

`flatpak --gl-drivers`
nvidia-465-27
default
host

**Problem description**
Looks like it needs the libnghttp2.so.14 library file. Could that be added?

```
Starting app 465020
>>> Adding process 570 for game ID 465020
GameAction [AppID 465020, ActionID 1] : LaunchApp changed task to WaitingGameWindow with ""
ERROR: ld.so: object '/home/joshua/.var/app/com.valvesoftware.Steam/.local/share/Steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
./SectorSix: error while loading shared libraries: libnghttp2.so.14: cannot open shared object file: No such file or directory
GameAction [AppID 465020, ActionID 1] : LaunchApp changed task to Completed with ""
>>> Adding process 571 for game ID 465020
Game removed: AppID 465020 "", ProcID 570
Uploaded AppInterfaceStats to Steam
Exiting app 465020
```

**Does this issue reproduce with native Steam**
Have not tested yet