style(tazjin/nixos/hidpi): Set DPI setting to 161

This results in a much more useful element size. Note that this still
does not scale some core UI elements, such as the mouse cursor, at all.

Change-Id: I7d4da485f0723740a7228a1561aaf50135c86032
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5575
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

users/tazjin/nixos/modules/hidpi.nix

@@ -13,5 +13,5 @@
   # Bump DPI across the board.
   # TODO(tazjin): This should actually be set per monitor, but I
   # haven't yet figured out the right interface for doing that.
-  services.xserver.dpi = 192;
+  services.xserver.dpi = 161;
 }