Fix Helm chart instructions for todo-backend quickstart

Issue description:

The todo-backend contains incorrect or outdated values for the EAPXPrelease code snippets.

Run the Backend on OpenShift -> Build and Deploy the Backend on OpenShift with Bootable Jar section:

1. --set build.ref=EAP_7.4.0.Final - this parameter value itself is not correct. In addition, from the user POV it would be clearer if we omit this parameter - as soon as the XP3 quickstarts are out, we are able to release https://raw.githubusercontent.com/jbossas/eap-charts/main/examples/eap-xp3/todo-backend/todo-backend-bootable-jar.yaml with correct build.ref value - there will be no reason to keep it in Helm command.

1. --set build.ref=EAP_7.4.0.Final - see the previous point.
2. wrong build.uri value (https://github.com/wildfly/quickstart.git) - it should be https://github.com/jboss-developer/jboss-eap-quickstarts.git - as it is in a previous Bootable jar section.

Architecture with S2I section:

1. there should be https://github.com/jbossas/eap-datasources-galleon-pack URL instead of https://github.com/wildfly-extras/wildfly-datasources-galleon-pack (since we are using org.jboss.eap:eap-datasources-galleon-pack feature pack).