yuzu/configure_filesystem: Remove "Select Cache Directory" option

This tab of the settings is already extremely bloated and the setting itself is quite useless.
With a gamelist of almost 30 games, the cache directory is smaller than 1MB for me and therefore I don't see why it needs to be configurable.

src/yuzu/configuration/configure_filesystem.h

@@ -32,7 +32,6 @@ private:
         Gamecard,
         Dump,
         Load,
-        Cache,
     };
 
     void SetDirectory(DirectoryTarget target, QLineEdit* edit);