feat: run pyupgrade

Hello dear contributors,

This is an auto generated modification to help you improve the code base of logilab. If this commit is bad don't hesitate to close this MR and report it here https://forge.extranet.logilab.fr/cubicweb/cube-doctor/-/issues.

Kind regards,

cubicweb_subprocess/entities.py

-# -*- coding: utf-8 -*-
 # copyright 2014-2022 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
 # contact http://www.logilab.fr -- mailto:contact@logilab.fr
 #
@@ -65,13 +64,14 @@ class Subprocess(AnyEntity):
     def _environ(self):
         env = os.environ.copy()
         env.update(json.loads(self.env) if self.env else {})
-        return dict(
-            (
-                k.encode(self.envencoding) if isinstance(k, str) else k,
-                v.encode(self.envencoding) if isinstance(v, str) else v,
-            )
+        return {
+            k.encode(self.envencoding)
+            if isinstance(k, str)
+            else k: v.encode(self.envencoding)
+            if isinstance(v, str)
+            else v
             for k, v in env.items()
-        )
+        }
 
     def _launch(self):
         """Launch a subprocess defined.