duplicity: remove invoke from dependencies

invoke is not a required dependency of duplicity.
It does not appear in upstream's requirements.txt nor pyproject.toml:
- https://gitlab.com/duplicity/duplicity/-/blob/dev/requirements.txt
- https://gitlab.com/duplicity/duplicity/-/blob/dev/pyproject.toml

pkgs/by-name/du/duplicity/package.nix

@@ -75,20 +75,17 @@ let
       glib
     ];
 
-    pythonPath =
-      with python3.pkgs;
-      [
-        b2sdk
-        boto3
-        idna
-        pygobject3
-        fasteners
-        paramiko
-        pexpect
-        # Currently marked as broken.
-        # pydrive2
-      ]
-      ++ paramiko.optional-dependencies.invoke;
+    pythonPath = with python3.pkgs; [
+      b2sdk
+      boto3
+      idna
+      pygobject3
+      fasteners
+      paramiko
+      pexpect
+      # Currently marked as broken.
+      # pydrive2
+    ];
 
     nativeCheckInputs = [
       gnupg # Add 'gpg' to PATH.