update yarn command

doc/update/8.16-to-8.17.md

@@ -118,7 +118,7 @@ sudo -u git -H bundle clean
 sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
 
 # Install/update frontend asset dependencies
-sudo -u git -H yarn install
+sudo -u git -H yarn install --force --pure-lockfile
 
 # Clean up assets and cache
 sudo -u git -H bundle exec rake gitlab:assets:clean gitlab:assets:compile cache:clear RAILS_ENV=production