Update docs/Formula-Cookbook.md

Co-authored-by: Mike McQuaid <[email protected]>

docs/Formula-Cookbook.md

@@ -334,7 +334,7 @@ test do
 end
 ```
 
-* If your program writes to sterr, you can [redirect sterr to stdout for assertions with `shell_output`](https://github.com/Homebrew/brew/issues/5149). For example:
+* If the binary only writes to `stderr`, you can redirect `stderr` to `stdout` for assertions with `shell_output`. For example:
 
 ```ruby
 test do