Specify proper repo URLs, add Chart.lock

Chart.lock

+dependencies:
+- name: nextcloud
+  repository: https://nextcloud.github.io/helm
+  version: 2.5.0
+- name: rabbitmq
+  repository: https://charts.bitnami.com/bitnami
+  version: 6.18.2
+- name: redis
+  repository: https://charts.bitnami.com/bitnami
+  version: 10.5.7
+- name: postgresql
+  repository: https://charts.bitnami.com/bitnami
+  version: 8.6.4
+digest: sha256:45a6835cd932a249a277aedbc0e1356437787ff1b8f7e883b4a30925a65a1719
+generated: "2021-03-18T09:14:11.008796323+01:00"

Chart.yaml

@@ -6,13 +6,13 @@ version: 0.2.4
 dependencies:
   - name: nextcloud
     version: 2.5.0
-    repository: "@nextcloud"
+    repository: "https://nextcloud.github.io/helm"
   - name: rabbitmq
     version: 6.18.2
-    repository: "@bitnami"
+    repository: "https://charts.bitnami.com/bitnami"
   - name: redis
     version: 10.5.7
-    repository: "@bitnami"
+    repository: "https://charts.bitnami.com/bitnami"
   - name: postgresql
     version: 8.6.4
-    repository: "@bitnami"
+    repository: "https://charts.bitnami.com/bitnami"