cicd: use epoch in .dev string

.ci/release.sh

@@ -3,7 +3,7 @@
 set -e
 
 git clean -fxd .
-_version=$(git describe --exact-match --tags HEAD || echo $(poetry version -s).dev$(date +%Y%m%d))
+_version=$(git describe --exact-match --tags HEAD || echo $(poetry version -s).dev$(date -u +%s))
 VERSION=${_version#'v'} # remove prefixed 'v' if any
 cp pyproject.toml /tmp/pyproject.toml.1
 poetry version ${VERSION}