Fix section header for stable branches and backports. All the other
headings end in a colon and have no blank lines between them and the
body of the section, so fix this one accordingly.
that valgrind generates nice output only on exit(), hence on shutdown
we don't execve() systemd-shutdown.
-STABLE BRANCHES AND BACKPORTS
-
+STABLE BRANCHES AND BACKPORTS:
Stable branches with backported patches are available in the
systemd-stable repo at https://github.com/systemd/systemd-stable.