fix(brew): suppress error message of brew cask on Linux (#11302)

plugins/brew/brew.plugin.zsh

@@ -36,7 +36,7 @@ alias buf='brew upgrade --formula'
 
 function brews() {
   local formulae="$(brew leaves | xargs brew deps --installed --for-each)"
-  local casks="$(brew list --cask)"
+  local casks="$(brew list --cask 2>/dev/null)"
 
   local blue="$(tput setaf 4)"
   local bold="$(tput bold)"