Sets release date for v1.1.0

Author: LordHepipud

doc/31-Changelog.md

@@ -7,7 +7,7 @@ documentation before upgrading to a new release.
 
 Released closed milestones can be found on [GitHub](https://github.com/Icinga/icinga-powershell-framework/milestones?state=closed).
 
-## 1.1.0 (pending)
+## 1.1.0 (2020-06-02)
 
 [Issue and PRs](https://github.com/Icinga/icinga-powershell-framework/milestone/4?closed=1)