Update iui.yml (#1559)

Author: dodoxxb

conference/HI/iui.yml

@@ -38,8 +38,8 @@
       id: iui27
       link: https://iui.hosting.acm.org/2027/
       timeline:
-        - abstract_deadline: 'TBD'
-          deadline: 'TBD'
+        - abstract_deadline: '2026-08-13 23:59:59'
+          deadline: '2026-08-20 23:59:59'
       timezone: AoE
       date: February 8-11, 2027
       place: Helsinki, Finland