Remove donation link from contributor guide (arduino#12093)

The Arduino company is no longer soliciting monetary donations. Community members who wish to contribute to the project
still have opportunities to do so via the other options listed in the contributor guide.

Author: per1234

CONTRIBUTING.md

@@ -8,7 +8,7 @@ Thanks for your interest in contributing to this free open source project! Ardui
 | - Bug fix<br/>- Enhancement | Pull Request (read the [pull request guidelines](#pull-requests)) |
 | Translations for the Arduino IDE | [transifex](https://www.transifex.com/mbanzi/arduino-ide-15/) |
 | Translations for the [Language Reference](https://www.arduino.cc/reference) | [Reference repositories](https://github.com/arduino?q=reference-) |
-| Monetary | - [Donate](https://www.arduino.cc/en/Main/Contribute)<br/>- [Buy official products](https://store.arduino.cc) |
+| Monetary | [Buy official products](https://store.arduino.cc) |
 
 
 ## Issues