Formally deprecate DEFAULT_FOLDER (#24836)

data/mappings/info_rules.hjson

@@ -55,5 +55,6 @@
     // Items we want flagged in lint
     "CTPC": {"info_key": "_deprecated.ctpc", "deprecated": true, "replace_with": "CONVERT_TO=proton_c"},
     "CONVERT_TO_PROTON_C": {"info_key": "_deprecated.ctpc", "deprecated": true, "replace_with": "CONVERT_TO=proton_c"},
+    "DEFAULT_FOLDER": {"info_key": "_deprecated.default_folder", "deprecated": true},
     "VIAL_ENABLE": {"info_key": "_invalid.vial", "invalid": true}
 }