fix recompile assets step in 9.0 upgrade guide to use yarn

doc/update/8.17-to-9.0.md

@@ -115,11 +115,11 @@ sudo -u git -H bundle clean
 # Run database migrations
 sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
 
-# Install/update frontend asset dependencies
-sudo -u git -H npm install --production
+# Update node dependencies and recompile assets
+sudo -u git -H bundle exec rake yarn:install gitlab:assets:clean gitlab:assets:compile RAILS_ENV=production NODE_ENV=production
 
-# Clean up assets and cache
-sudo -u git -H bundle exec rake gitlab:assets:clean gitlab:assets:compile cache:clear RAILS_ENV=production
+# Clean up cache
+sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
 ```
 
 **MySQL installations**: Run through the `MySQL strings limits` and `Tables and data conversion to utf8mb4` [tasks](../install/database_mysql.md).