games/wesnoth: update to 1.18.6 release (+)

Version 1.18.6:
Multiplayer

• 5p - The Wilderlands:
• Fixed lag during AI turn (issue #10419)

Translations

• Updated translations: Ancient Greek, Arabic, Bengali, British English, Catalan, Chinese (Simplified), Czech, Finnish, French, Galician, Hungarian, Polish, Spanish

User interface

• The load-game dialog can now see the directories used by the development version (1.19.2 and later)