[NOT FOR MERGE] Test enabling Copy-on-Write by default

pandas/core/config_init.py

@@ -476,7 +476,7 @@ def use_inf_as_na_cb(key) -> None:
         "copy_on_write",
         # Get the default from an environment variable, if set, otherwise defaults
         # to False. This environment variable can be set for testing.
-        os.environ.get("PANDAS_COPY_ON_WRITE", "0") == "1",
+        True,
         copy_on_write_doc,
         validator=is_bool,
     )