Remove all the "prepare override"

[edevosc2c]

Not necessary anymore once georchestra/georchestra#4030 will be backported in 23.

All the instance where there are stuff like this:

• helm-georchestra/templates/cas/cas-deployment.yaml

  Line 30 in fb0f163

  - name: prepare-cas-webapp

• helm-georchestra/templates/geonetwork/geonetwork-deployment.yaml

  Line 41 in fb0f163

  - name: prepare-geonetwork-webapp

• helm-georchestra/templates/security-proxy/security-proxy-deployment.yaml

  Line 53 in fb0f163

  - name: prepare-proxy-webapp

• helm-georchestra/templates/geoserver/geoserver-deployment.yaml

  Line 46 in fb0f163

  - name: prepare-geoserver-webapp

Additional note: we recently discovered that due to the high usage of emptyDir, some Kubernetes node with a low amount of allocable emptyDir failed to schedule pods and would have pods crashing.

Detailed explanation of the problem in French: