future first: switch the order of some if statements (#5206)

Since we're adding this to our contribution guidelines in
https://github.com/python/typeshed/pull/5205

stdlib/ssl.pyi

@@ -228,16 +228,16 @@ class _ASN1Object(NamedTuple):
     longname: str
     oid: str
 
-if sys.version_info < (3,):
-    class Purpose(_ASN1Object):
-        SERVER_AUTH: ClassVar[Purpose]
-        CLIENT_AUTH: ClassVar[Purpose]
-
-else:
+if sys.version_info >= (3, 0):
     class Purpose(_ASN1Object, enum.Enum):
         SERVER_AUTH: _ASN1Object
         CLIENT_AUTH: _ASN1Object
 
+else:
+    class Purpose(_ASN1Object):
+        SERVER_AUTH: ClassVar[Purpose]
+        CLIENT_AUTH: ClassVar[Purpose]
+
 class SSLSocket(socket.socket):
     context: SSLContext
     server_side: bool