Use version 4.0 no need to bump yet

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Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

CHANGELOG.rst

@@ -7,7 +7,7 @@ next
 ----
 
 
-4.1 (2022-05-05)
+4.0 (2022-05-05)
 ----------------
 
 * API changes

setup.py

@@ -24,7 +24,7 @@
 
 setup(
     name="boolean.py",
-    version="4.1",
+    version="4.0",
     license="BSD-2-Clause",
     description="Define boolean algebras, create and parse boolean "
     "expressions and create custom boolean DSL.",