Change ICIC 2026 deadline to March 21 (#1441)

Updated the deadline for the ICIC 2026 conference.

Author: Lukangkang123

conference/MX/icic.yml

@@ -27,7 +27,7 @@
       id: icic26
       link: http://www.ic-icc.cn/2026/
       timeline:
-        - deadline: '2026-03-20 11:59:59'
+        - deadline: '2026-03-21 11:59:59'
       timezone: UTC+8
       date: July 22-26, 2026
       place: Toronto, Canada