feat: add specific minor version of alpine helper container

Author: tzabbi

charts/plex-media-server/values.yaml

@@ -93,7 +93,7 @@ initContainer:
     registry: index.docker.io
     repository: alpine
     # -- If unset use latest
-    tag: 3
+    tag: 3.21
     sha: ""
     pullPolicy: IfNotPresent