Revert "Upgrade to the latest version of openvpn3"

This reverts commit 6a1adb0.

Unfortunately, openvpn3 v21 has some bugs with DNS search domains, see
OpenVPN/openvpn3-linux#208 (comment)
for details.

flake.nix

@@ -198,11 +198,6 @@
                   url = "https://github.com/jfly/nixpkgs/commit/653dd896a6cb28f2bc206dc8566348e649bea7d4.patch";
                   hash = "sha256-/NJqA1zYJ+uYMQ3tV9zyUG6n4LqeIjcyvvfSr07BVps=";
                 })
-                (unpatched.fetchpatch {
-                  name = "openvpn3: 20 -> 21";
-                  url = "https://github.com/NixOS/nixpkgs/pull/295058.patch";
-                  hash = "sha256-P7HMaybI8AdK/41JzucSUq7i3rg1Q+jOvt0ScmilNWo=";
-                })
               ];
             };
           };

shared/polybar-openvpn3/default.nix

@@ -8,5 +8,15 @@ with pkgs.python3Packages; buildPythonApplication {
   nativeBuildInputs = [ setuptools ];
   src = ./.;
 
-  propagatedBuildInputs = pkgs.openvpn3.pythonPath ++ [ pkgs.openvpn3 ];
+  propagatedBuildInputs = pkgs.openvpn3.pythonPath ++ [
+    (pkgs.openvpn3.overrideAttrs (oldAttrs: {
+      patches = [
+        # TODO: remove this when v21 of openvpn3 lands on nixpkgs-unstable.
+        (pkgs.fetchpatch {
+          url = "https://github.com/OpenVPN/openvpn3-linux/commit/ba6fe37e7e28d1e633b56052383da3072f03c11e.patch";
+          sha256 = "sha256-MBXDEfeyg0VQGp9GYcpTZyLB0h6LX1qlaqZSDhOAJgQ=";
+        })
+      ];
+    }))
+  ];
 }