fix(vds-nftables): remove allowPing — not a top-level networking option

networking.allowPing was a top-level networking option when
firewall.enable = true. With firewall.enable = false (T3 Option A),
the option no longer exists at the networking level. ICMP is now
handled by the nftables ruleset directly
().

Rebuild error: 'The option networking.allowPing does not exist.
Definition values: networking.domain, networking.vlans, networking.wicd.'

Fix: remove the line. No behavior change — ICMP is still accepted
via nftables.

configurations/vds.nix

@@ -89,7 +89,10 @@
     firewall.enable = false;
     firewall.allowedTCPPorts = lib.mkForce [ ];
     firewall.interfaces = lib.mkForce { };
-    allowPing = true;
+    # allowPing removed 2026-10-10 (T3 Option A): with firewall.enable = false,
+    # `networking.allowPing` no longer exists as a top-level option. ICMP
+    # accept is now handled by the nftables ruleset below
+    # (`ip protocol icmp accept`).
     nftables = {
       enable = true;
       ruleset = ''