crash-handler: Add back notice log message

Fixes https://github.com/systemd/systemd/pull/33959#discussion_r1730987738

src/core/crash-handler.c

@@ -155,6 +155,8 @@ _noreturn_ static void crash(int sig, siginfo_t *siginfo, void *context) {
         (void) sigaction(SIGCHLD, &sa, NULL);
 
         if (arg_crash_shell) {
+                log_notice("Executing crash shell...");
+
                 pid = raw_clone(SIGCHLD);
                 if (pid < 0)
                         log_struct_errno(LOG_EMERG, errno,