[Composer] redirect stderr to /dev/null for completion commands

plugins/composer/composer.plugin.zsh

@@ -7,11 +7,11 @@
 
 # Composer basic command completion
 _composer_get_command_list () {
-    $_comp_command1 --no-ansi | sed "1,/Available commands/d" | awk '/^[ \t]*[a-z]+/ { print $1 }'
+    $_comp_command1 --no-ansi 2>/dev/null | sed "1,/Available commands/d" | awk '/^[ \t]*[a-z]+/ { print $1 }'
 }
 
 _composer_get_required_list () {
-    $_comp_command1 show -s --no-ansi | sed '1,/requires/d' | awk 'NF > 0 && !/^requires \(dev\)/{ print $1 }'
+    $_comp_command1 show -s --no-ansi 2>/dev/null | sed '1,/requires/d' | awk 'NF > 0 && !/^requires \(dev\)/{ print $1 }'
 }
 
 _composer () {