`bwrap: unshare user ns: No space left on device`

Hi,

I recently wrote a [bwrap script for Firefox in bash](https://gitlab.com/TheEvilSkeleton/bubblewrap/-/blob/main/firefox). However, whenever I try to launch it like a normal script or binary, I get the following error:
```
bwrap: unshare user ns: No space left on device
```

This issue is only reproducible on my laptop apparently. The script ran without a problem on my desktop. Both systems use Fedora Silverblue 35.

I don't know if it's a hardware issue, so I am sharing my laptop's and desktop's specs:
- laptop: https://linux-hardware.org/?probe=d136f5d8f7
- desktop: https://linux-hardware.org/?probe=ad0a5b8c83

(Just to be clear, these are old hardware probes, but the specs are the same.)

I wasn't able to retrieve any logs because I couldn't find a `--verbose` flag.

I came across https://github.com/containers/bubblewrap/issues/371. I checked `max_user_namespaces` and I have the following:
```bash
[root@TheMainLaptop ~]# cat /proc/sys/user/max_user_namespaces
28906
```

Also, I didn't run the script as root.