chore: add deprecation of copy_on_write_X

Author: ilan-gold

src/anndata/_settings.py

@@ -398,7 +398,7 @@ def __doc__(self):
 
 
 settings = SettingsManager()
-
+settings.deprecate("copy_on_write_X", "0.14")
 ##################################################################################
 # PLACE REGISTERED SETTINGS HERE SO THEY CAN BE PICKED UP FOR DOCSTRING CREATION #
 ##################################################################################
@@ -517,7 +517,7 @@ def validate_sparse_settings(val: Any, settings: SettingsManager) -> None:
 
 settings.register(
     "copy_on_write_X",
-    default_value=False,
+    default_value=True,
     description=(
         "Whether to copy-on-write X. "
         "Currently `my_adata_view[subset].X = value` will write back to the original AnnData object at the `subset` location. "