update version in release notes

Author: mgravell

docs/ReleaseNotes.md

@@ -8,6 +8,10 @@ Current package versions:
 
 ## Unreleased
 
+- nothing yet
+
+## 2.8.58
+
 - Fix [#2679](https://github.com/StackExchange/StackExchange.Redis/issues/2679) - blocking call in long-running connects ([#2680 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2680))
 - Support async cancellation of `SCAN` enumeration ([#2911 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2911)) 
 - Add `XTRIM MINID` support ([#2842 by kijanawoodard](https://github.com/StackExchange/StackExchange.Redis/pull/2842))