rolling release: Add timestamp to version numbers (#39701)

Apparently Atomic doesn't just pick the latest release, they also
require that the new version number compares greater than the old one as
measured by `version_compare()`. So we'll have to throw a timestamp in
after all.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/11259970748

Upstream-Ref: Automattic/jetpack@77c7a79

.github/files/autorelease.sh

@@ -28,7 +28,7 @@ elif [[ "$GITHUB_REF" == "refs/heads/trunk" ]]; then
 	fi
 	ROLLING_MODE=true
 	CURRENT_VER=$( sed -nEe 's/^## \[?([^]]*)\]? - .*/\1/;T;p;q' CHANGELOG.md || true )
-	GIT_SUFFIX=$( git log -1 --format=%h . )
+	GIT_SUFFIX=$( git log -1 --format="%ct.g%h" . )
 	TAG="$CURRENT_VER+rolling.$GIT_SUFFIX"
 else
 	echo "::error::Expected GITHUB_REF like \`refs/tags/v1.2.3\` or \`refs/tags/1.2.3\` or \`refs/heads/trunk\` for rolling releases, got \`$GITHUB_REF\`"