Fix example in docs (#994)

Updated environment.md example command using cowsay. Cowsay commands now need a -t flag in version 6+

docs/environment.md

@@ -78,7 +78,7 @@ Hatch ensures that environments are always compatible with the currently defined
 For example, add `cowsay` as a dependency then try to run it:
 
 ```console
-$ hatch run cowsay "Hello, world!"
+$ hatch run cowsay -t "Hello, world!"
 Syncing dependencies
   _____________
 | Hello, world! |