fix(config): remove the retired permission migration schema row (CW-7890)

Root review found the removed Ask-to-Accept-Edits migration still declared a setting with no runtime owner. Remove its final schema consumer rather than advertise a dead setting.

Root cached macOS checks: 4 settings-schema tests passed, 0 failed; explicit saved-choice Runtime regression 1 passed, 0 failed. Worker proof on the same mode behavior: macOS TUI 8/0, Runtime 1/0; Linux TUI 7/0, Runtime 1/0; rebased preflight 8 checks passed. Ordinary source whitespace passes; four fixed-width footer goldens retain validated trailing cell padding. No installed or release acceptance claimed.

crates/config/src/settings_schema.rs

@@ -1552,12 +1552,6 @@ pub const SETTINGS_SCHEMA: &[SettingDef] = &[
         "false",
         None,
     ),
-    def(
-        "ask_to_accept_edits_migrated",
-        SettingKind::Bool(ON_OFF),
-        "false",
-        None,
-    ),
     def("behavioral_tip_impressions", SettingKind::String, "", None),
     // Footer key-hint use counts: a hint retires to its bare state once its
     // binding has been used enough times. Written by the footer, never edited.