These maps should be copied into the maps folder inside your StarCraft II folder (Default SC2 location is C:\Program Files (x86)\StarCraft II\ on Windows). If there is not a "maps" folder there already, you must create it, and put the maps there.
Note for linux users: the folder name is case sensitive.
This map is different to the Flat48 map found in the Blizzard repos because it changes the map from being a 4 player spawn map instead to a 2 player spawn map.
The AI Arena ladder utilizes a Linux server for running games. As StarCraft 2 is not actively supported on Linux, updates are not automatically applied, leading to discrepancies between the AI bot ladder and the human ladder on Battle.net. However, these discrepancies can be addressed to some extent by manually updating the maps.
Please follow the steps outlined in this documentation to update your maps: StarCraft 2 Patch for Linux.