chore(deps): update longhornio/longhorn-manager docker tag to v1.8.0

kubernetes/longhorn/helm/values.yaml

@@ -6,7 +6,7 @@ image:
       tag: "v1.8.0"
     manager:
       repository: "longhornio/longhorn-manager"
-      tag: "v1.7.2"
+      tag: "v1.8.0"
     ui:
       repository: "longhornio/longhorn-ui"
       tag: "v1.7.2"