Update README.md (#7059)

Fix donate link

Author: kbodwin

README.md

@@ -19,7 +19,7 @@
 
 The `data.table` project uses a [custom governance agreement](./GOVERNANCE.md) 
 and is fiscally sponsored by [NumFOCUS](https://numfocus.org/). Consider making 
-a [tax-deductible donation](https://numfocus.org/donate-to-data-table) to help the project 
+a [tax-deductible donation](https://numfocus.org/project/data-table) to help the project 
 pay for developer time, professional services, travel, workshops, and a variety of other needs.
 
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