chore(ci): Fix duplicate volume mount for postgres in E2E tests

[oguzhand95]

Previously an update to the bitnami/postgres chart broke E2E tests because a data volume wasn't mounted which #2061 fixed. With the recent update, it is now mounted and we get a duplicate entry error:

Events:
  Type     Reason        Age                  From                    Message
  ----     ------        ----                 ----                    -------
  Warning  FailedCreate  25s (x15 over 107s)  statefulset-controller  create Pod postgres-0 in StatefulSet postgres failed error: Pod "postgres-0" is invalid: spec.containers[0].volumeMounts[7].mountPath: Invalid value: "/bitnami/postgresql": must be unique

This PR removes the previously added volume mount entry to solve the problem.