sysext: fix --help indenting/line breaking

Let's make sure there's an empty line after the explanatory text like we
usually do it, and do not indent the 2nd line more than the 1st

src/sysext/sysext.c

@@ -1371,8 +1371,9 @@ static int verb_help(int argc, char **argv, void *userdata) {
                 return log_oom();
 
         printf("%1$s [OPTIONS...] COMMAND\n"
-                "\n%5$sMerge extension images into /usr/ and /opt/ hierarchies for\n"
-               " sysext and into the /etc/ hierarchy for confext.%6$s\n"
+               "\n%5$sMerge extension images into /usr/ and /opt/ hierarchies for\n"
+               "sysext and into the /etc/ hierarchy for confext.%6$s\n"
+               "\n%3$sCommands:%4$s\n"
                "  status                  Show current merge status (default)\n"
                "  merge                   Merge extensions into relevant hierarchies\n"
                "  unmerge                 Unmerge extensions from relevant hierarchies\n"