Fix: Kubo 33.2 crashed on Ubuntu 22.04

Due to an error reading the denylist.

The error was:
```
Error: constructing the node (see log for full detail):
error walking /home/ipfs/.config/ipfs/denylists:
lstat /home/ipfs/.config/ipfs/denylists: permission denied
```

The [documentation](https://specs.ipfs.tech/compact-denylist-format/)
mentions that:

> Implementations SHOULD look in /etc/ipfs/denylists/ and
> $XDG_CONFIG_HOME/ipfs/denylists/ (default: ~/.config/ipfs/denylists)
> for denylist files.

I am not sure why this only failed on Ubuntu 22.04
and not Debian 12 or Ubuntu 24.04. My first assumption
would be a difference in Systemd.

Author: hoh

packaging/aleph-vm/etc/systemd/system/ipfs.service

@@ -58,6 +58,10 @@ CapabilityBoundingSet=CAP_NET_BIND_SERVICE
 # enable to specify a higher limit for open files/connections
 #LimitNOFILE=1000000
 
+# Avoid a permission denier error when running `lstat /home/ipfs/.config/ipfs/denylists`
+# due to checking $XDG_CONFIG_HOME/ipfs/denylists/
+Environment=XDG_CONFIG_HOME=/etc
+
 #don't use swap
 MemorySwapMax=0