Remove fortress and tower entity limits.

The distance requirement is enough:
These entity limits for fortresses and towers unnecessarily restrict player freedom, especially on giant-size maps. See also comments by various people on the forums (e.g. https://wildfiregames.com/forum/topic/37687-lets-fight-gameplay-balance-mod/page/2/?tab=comments#comment-422251).

Patch by: @Nescio
Rebased by: @marder
Differential revision: https://code.wildfiregames.com/D3778
Reviewed by: @borg-, @chrstgtr
Comment from: @wowgetoffyourcellphone