Cannot use host system's shell in integrated terminal

Hi there!

Just installed VS Code via Flatpak on my Fedora Silverblue 33. Everything's working pretty fine so far, except for the following detail.
When first opening VS Code, we are presented with this `flatpak-warning.txt`. That's actually really appreciated.
However, one of its suggestions is to use the following to use the host system's shell:

```
To make the Integrated Terminal automatically use the host system's shell,
you can add this to the settings:

{
"terminal.integrated.shell.linux": "/usr/bin/env",
"terminal.integrated.shellArgs.linux": ["--", "flatpak-spawn", "--host", "bash"]
}
```

That did not work. So I went back to the default and tried this (in the integrated terminal):

```sh
sh-5.1$ flatpak-spawn --host echo hey
Can't find bus: Cannot autolaunch D-Bus without X11 $DISPLAY
```

Since `$DISPLAY` is defined in the host, I went ahead and ran:

```sh
sh-5.1$ DISPLAY=:0 flatpak-spawn --host echo hey
Can't find bus: Failed to execute child process “dbus-launch” (No such file or directory)
```

Is there anything I can do to make it work?