Update soda.yml (#1434)

Author: dodoxxb

conference/CT/soda.yml

@@ -27,7 +27,7 @@
       id: soda27
       link: https://www.siam.org/conferences-events/siam-conferences/soda27/
       timeline:
-        - deadline: 'TBD'
+        - deadline: '2026-07-09 23:59:59'
       timezone: UTC-12
       date: January 24-27, 2027
       place: Philadelphia, Pennsylvania, USA