Adjust setting texts for show running costs per year setting

src/lang/extra/english.txt

@@ -339,8 +339,8 @@ STR_CONFIG_SETTING_HIDE_DEFAULT_STOP_LOCATION_HELPTEXT          :When enabled, h
 STR_CONFIG_SHOW_RAIL_POLYLINE_TOOL                              :Show rail polyline tool: {STRING2}
 STR_CONFIG_SHOW_RAIL_POLYLINE_TOOL_HELPTEXT                     :When enabled, the rail construction toolbar includes a button to build using the polyline mode.
 
-STR_CONFIG_SHOW_VEHICLE_RUNNING_COSTS_CALENDAR_YEAR             :Show vehicle running costs per calendar year: {STRING2}
-STR_CONFIG_SHOW_VEHICLE_RUNNING_COSTS_CALENDAR_YEAR_HELPTEXT    :When using a day length factor greater than one, show vehicle running costs per calendar year instead of per original year.
+STR_CONFIG_SHOW_VEHICLE_RUNNING_COSTS_CALENDAR_YEAR             :Show vehicle running costs calendar year/period: {STRING2}
+STR_CONFIG_SHOW_VEHICLE_RUNNING_COSTS_CALENDAR_YEAR_HELPTEXT    :When using a day length factor greater than one, show vehicle running costs per calendar year (in calendar mode) or per period (in wallclock mode) instead of per original year.
 
 STR_CONFIG_SETTING_ADV_SIG_BRIDGE_TUN_MODES                     :Enable signals on bridges/tunnels advanced modes: {STRING2}
 STR_CONFIG_SETTING_ADV_SIG_BRIDGE_TUN_MODES_HELPTEXT            :Enables use of advanced modes of signal simulation on bridges and tunnels. When disabled, bridges/tunnels which are not already in an advanced mode cannot be changed to an advanced mode, however other players may choose to enable this setting and use an advanced mode.