Axe cav minor buff.
Gives them 8.7 Hack DPS since they are too weak currently.
Original patch by: @real_tabasco_sauce at https://gitlab.com/0ad/0ad-community-mod-a26/-/merge_requests/11.
Ported by: @vv221
Differential revision: https://code.wildfiregames.com/D4862
Comments by: @chrstgtr, majima