changelog: fix missing link for 1.8.2 (#6199)

Author: Darksonn

tokio/CHANGELOG.md

@@ -1547,7 +1547,9 @@ Fixes a missed edge case from 1.8.1.
 
 ### Fixed
 
-- runtime: drop canceled future on next poll (#3965)
+- runtime: drop canceled future on next poll ([#3965])
+
+[#3965]: https://github.com/tokio-rs/tokio/pull/3965
 
 # 1.8.1 (July 6, 2021)