Add closing bracket

Author: LorenzNickel

docs/os.md

@@ -4,7 +4,7 @@ _WARNING:_ These functions can lead to information leakage if not used
 appropriately.
 
 _WARNING:_ Some notable implementations of Sprig (such as
-[Kubernetes Helm](http://helm.sh) _do not provide these functions for security
+[Kubernetes Helm](http://helm.sh)) _do not provide these functions for security
 reasons_.
 
 ## env