fix(e2e): use correct image name in kustomize overlay

Closes #840

The e2e kustomize overlay matches
docker.io/library/plugin-barman-cloud but the base kustomization at
kubernetes/kustomization.yaml matches the bare plugin-barman-cloud
name from kubernetes/deployment.yaml and replaces it with the GHCR
image. Since the overlay name never matches, the locally-built image
is never deployed and e2e tests always run against the main branch
code from GHCR.

Use the bare image name so the overlay rule overrides the base rule.

Broken since b7daaac (#89) changed the base kustomization's newName
from docker.io/library/plugin-barman-cloud to the GHCR image without
updating the e2e overlay.

Signed-off-by: Marco Nenciarini <marco.nenciarini@enterprisedb.com>

Author: mnencia

test/e2e/e2e_suite_test.go

@@ -60,7 +60,7 @@ var _ = SynchronizedBeforeSuite(func(ctx SpecContext) []byte {
 		Resources: []string{barmanCloudKustomizationPath},
 		Images: []kustomizeTypes.Image{
 			{
-				Name:    "docker.io/library/plugin-barman-cloud",
+				Name:    "ghcr.io/cloudnative-pg/plugin-barman-cloud-testing",
 				NewName: "registry.barman-cloud-plugin:5000/plugin-barman-cloud",
 				NewTag:  "testing",
 			},