games/freeciv: update to 2.6.5 bugfix release

Notably it fixes regression in 2.6.4 gtk3-client that present units in city dialog had no overlays drawn at all.

Release Notes: https://freeciv.fandom.com/wiki/NEWS-2.6.5

(cherry picked from commit b88d50dd0c092101134d42489c0a92f5f33926b4)