Improve text for rename station extra functionality tooltip

src/lang/extra/english.txt

@@ -2098,7 +2098,7 @@ STR_REFIT_SHIP_PART                                             :Part {NUM}
 
 STR_VERY_REDUCED                                                :Very reduced
 
-STR_STATION_VIEW_RENAME_TOOLTIP_EXTRA                           :{BLACK}{STRING}{}(Ctrl+Click "{STRING}" button to generate new default name).{}{}Ctrl+Click to exchange name with another station.
+STR_STATION_VIEW_RENAME_TOOLTIP_EXTRA                           :{BLACK}{STRING}{}(Ctrl+Click "{STRING}" button to generate a new default name).{}{}Ctrl+Click to exchange names with another station.
 STR_ERROR_CAN_T_EXCHANGE_STATION_NAMES                          :{WHITE}Can't exchange station names...
 STR_ERROR_STATIONS_NOT_IN_SAME_TOWN                             :{WHITE}... stations are not in the same town
 STR_ERROR_STATION_ATTACHED_TO_INDUSTRY                          :{WHITE}... station is attached to an industry