Remove donation link from contributor guide

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

docs/CONTRIBUTING.md

@@ -4,19 +4,18 @@ First of all, thanks for contributing! This document provides some basic guideli
 
 There are several ways you can get involved:
 
-| Type of contribution                              | Contribution method                                     |
-| ------------------------------------------------- | ------------------------------------------------------- |
-| - Support request<br/>- Question<br/>- Discussion | Post on the [Arduino Forum][forum]                      |
-| - Bug report<br/>- Feature request                | Issue report (read the [issue guidelines][issues])      |
-| Beta testing                                      | Try out the [nightly build][nightly]                    |
-| - Bug fix<br/>- Enhancement                       | Pull Request (read the [pull request guidelines][prs])  |
-| Monetary                                          | - [Donate][donate]<br/>- [Buy official products][store] |
+| Type of contribution                              | Contribution method                                    |
+| ------------------------------------------------- | ------------------------------------------------------ |
+| - Support request<br/>- Question<br/>- Discussion | Post on the [Arduino Forum][forum]                     |
+| - Bug report<br/>- Feature request                | Issue report (read the [issue guidelines][issues])     |
+| Beta testing                                      | Try out the [nightly build][nightly]                   |
+| - Bug fix<br/>- Enhancement                       | Pull Request (read the [pull request guidelines][prs]) |
+| Monetary                                          | [Buy official products][store]                         |
 
 [forum]: https://forum.arduino.cc/c/using-arduino/project-guidance/19
 [issues]: #issue-reports
 [nightly]: installation.md#nightly-builds
 [prs]: #pull-requests
-[donate]: https://www.arduino.cc/en/donate/
 [store]: https://store.arduino.cc
 
 ## Issue Reports