Fix: store autosave settings under the new names

src/table/settings/gui_settings.ini

@@ -16,7 +16,6 @@ static void InvalidateNewGRFChangeWindows(int32 new_value);
 static void ZoomMinMaxChanged(int32 new_value);
 static void SpriteZoomMinChanged(int32 new_value);
 
-static constexpr std::initializer_list<const char*> _autosave_interval{"off", "monthly", "quarterly", "half year", "yearly"};
 static constexpr std::initializer_list<const char*> _osk_activation{"disabled", "double", "single", "immediately"};
 static constexpr std::initializer_list<const char*> _savegame_date{"long", "short", "iso"};
 
@@ -48,16 +47,15 @@ extra    = 0
 startup  = false
 
 
-[SDTC_OMANY]
-var      = gui.autosave
-type     = SLE_UINT8
-flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_GUI_DROPDOWN
-def      = 1
-max      = 4
-full     = _autosave_interval
+[SDTC_VAR]
+var      = gui.autosave_interval
+type     = SLE_UINT32
+flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC
+def      = 10
+min      = 0
+max      = 1440
 str      = STR_CONFIG_SETTING_AUTOSAVE
 strhelp  = STR_CONFIG_SETTING_AUTOSAVE_HELPTEXT
-strval   = STR_GAME_OPTIONS_AUTOSAVE_DROPDOWN_OFF
 cat      = SC_BASIC
 
 [SDTC_BOOL]

src/table/settings/old_gameopt_settings.ini

@@ -142,15 +142,6 @@ min      = MIN_SNOWLINE_HEIGHT * TILE_HEIGHT
 max      = UINT8_MAX
 to       = SLV_22
 
-[SDTC_OMANY]
-var      = gui.autosave
-type     = SLE_UINT8
-flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC
-def      = 1
-max      = 4
-full     = _autosave_interval
-cat      = SC_BASIC
-
 [SDT_OMANY]
 var      = vehicle.road_side
 type     = SLE_UINT8