readahead: wipe out readahead

shell-completion/zsh/_systemd

@@ -63,8 +63,7 @@ case "$service" in
             '--ready[Inform the init system about service start-up completion.]' \
             '--pid=[Inform the init system about the main PID of the daemon]' \
             '--status=[Send a free-form status string for the daemon to the init systemd]' \
-            '--booted[Returns 0 if the system was booted up with systemd]' \
-            '--readahead=[Controls disk read-ahead operations]:arguments:(cancel done noreply)'
+            '--booted[Returns 0 if the system was booted up with systemd]'
     ;;
     systemd-tty-ask-password-agent)
         _arguments \