docs: remove footnote linking beaglebone issue

The footnote has not been rendered correctly on npm and
flows.nodered.org

README.md

@@ -15,9 +15,7 @@ We introduce "coap request", "coap in", and "coap response" nodes which can be u
 ## Requirements
 
 This module requires at least Node version 12.
-This might require you to upgrade the pre-installed Node version on platforms like Beaglebone[^1]
-
-[^1]: See [this issue comment](https://github.com/JKRhb/node-red-contrib-coap/issues/40#issuecomment-1086693878) for information on how to upgrade the node version on BeagleBone.
+This might require you to upgrade the pre-installed Node version on platforms like Beaglebone.
 
 ## Install