[denonmarantz] Update protocol reference in readme (#10044)

Signed-off-by: Hilbrand Bouwkamp <hilbrand@h72.nl>

bundles/org.openhab.binding.denonmarantz/README.md

@@ -121,5 +121,4 @@ These resources can be useful to learn what to send using the `command`channel:
 - [AVR-X2000/E400](http://www2.aerne.com/Public/dok-sw.nsf/0c6187bc750a16fcc1256e3c005a9740/96a2ba120706d10dc1257bdd0033493f/$FILE/AVRX2000_E400_PROTOCOL(10.1.0)_V04.pdf)
 - [AVR-X4000](https://usa.denon.com/us/product/hometheater/receivers/avrx4000?docname=AVRX4000_PROTOCOL(10%203%200)_V03.pdf)
 - [AVR-3311CI/AVR-3311/AVR-991](https://www.awe-europe.com/documents/Control%20Docs/Denon/Archive/AVR3311CI_AVR3311_991_PROTOCOL_V7.1.0.pdf)
-- [CEOL Piccolo DRA-N5/RCD-N8](http://www.audioproducts.com.au/downloadcenter/products/Denon/CEOLPICCOLOBK/Manuals/DRAN5_RCDN8_PROTOCOL_V.1.0.0.pdf)
-- [Marantz Control Protocol (2014+)](http://m.us.marantz.com/DocumentMaster/US/Marantz%202014%20NR%20Series%20-%20SR%20Series%20RS232%20IP%20Protocol.xls)
+- [Denon/Marantz Control Protocol] (http://assets.eu.denon.com/DocumentMaster/DE/AVR1713_AVR1613_PROTOCOL_V8.6.0.pdf)