Added changelog

Author: papafe

source/unified-test-format/unified-test-format.md

@@ -3438,6 +3438,8 @@ other specs *and* collating spec changes developed in parallel or during the sam
 
 ## Changelog
 
+- 2025-10-22: Added `getSnapshotTime` operation on sessions.
+
 - 2025-09-16: **Schema version 1.26.** Add `awaitMinPoolSize` client parameter to await on connection pool population.
 
 - 2025-09-15: Remove note about Atlas Data Lake since Atlas Data Lake testing is removed.