Cloud's version of which doesn't support -s (#12080)

so we removed -s and sent the output to the dark place

tools/bin/deploy_docusaurus

@@ -31,7 +31,7 @@ pwd
 
 
 # Yarn check (which is commonly used to check for program existance)
-if ! which -s yarn; then
+if ! which yarn > /dev/null; then
   echo -e "$red_text""yarn not found HALP!!\n\n""$default_text"
   exit 1
 fi