[change] Unpinned system packages

Alpine repositories only contain one version of
the system package. Pinning dependencies provides
little to no benefit and result in failing CI
builds when old packages are yanked.

images/openwisp_nfs/Dockerfile

@@ -2,8 +2,8 @@ FROM alpine:3.20
 
 # hadolint ignore=DL3018
 RUN apk add --no-cache --update --verbose \
-            tzdata~=2024a-r0 \
-            nfs-utils~=2.6.1-r1 && \
+            tzdata \
+            nfs-utils && \
     rm -rf /var/cache/apk/* /tmp/*
 
 COPY ./openwisp_nfs/init_command.sh /init_command.sh