Try a different way to allow pre-releases in tox

Author: thibaudcolas

tox.ini

@@ -20,7 +20,7 @@ deps =
     dj42: Django>=4.2,<5.0
     dj50: Django>=5.0,<5.1
     dj51: Django>=5.1,<5.2
-    dj52: --pre Django>=5.2rc1,<6.0
+    dj52: Django>=5.2rc1,<6.0
     djmain: https://github.com/django/django/archive/main.zip
 
 [testenv:lint]