homestead: repair sed regex (#8103)

plugins/homestead/homestead.plugin.zsh

@@ -1,6 +1,6 @@
 # Homestead basic command completion
 _homestead_get_command_list () {
-  homestead --no-ansi | sed "1,/(Available|Common) commands/d" | awk '/^ +[a-z]+/ { print $1 }'
+  homestead --no-ansi | sed -E "1,/(Available|Common) commands/d" | awk '/^ +[a-z]+/ { print $1 }'
 }
 
 _homestead () {