upgrade alpine base image from v3.20.3 to v3.21.0 including upgrade of postsrsd package

https://github.com/roehling/postsrsd/blob/main/CHANGELOG.rst
https://git.alpinelinux.org/aports/commit/community/postsrsd?h=3.21-stable&id=cccbc96a196425fabfeff3eac25a7c1179db7cfb

Dockerfile

@@ -1,8 +1,8 @@
-FROM docker.io/alpine:3.20.3
+FROM docker.io/alpine:3.21.0
 
 # https://github.com/roehling/postsrsd/blob/main/CHANGELOG.rst
-# https://git.alpinelinux.org/aports/log/community/postsrsd?h=3.20-stable
-ARG POSTSRSD_PACKAGE_VERSION=2.0.9-r0
+# https://git.alpinelinux.org/aports/log/community/postsrsd?h=3.21-stable
+ARG POSTSRSD_PACKAGE_VERSION=2.0.10-r0
 RUN adduser -S postsrsd \
     && apk add --no-cache postsrsd=$POSTSRSD_PACKAGE_VERSION \
     && mkdir -p /etc/postsrsd/secrets \