DOC: Update donation links

Author: shoyer

README.rst

@@ -97,7 +97,7 @@ to supporting the open source scientific computing community. If you like
 Xarray and want to support our mission, please consider making a donation_
 to support our efforts.
 
-.. _donation: https://www.flipcause.com/secure/cause_pdetails/NDE2NTU=
+.. _donation: https://numfocus.salsalabs.org/donate-to-xarray/
 
 History
 -------

doc/index.rst

@@ -140,7 +140,7 @@ to supporting the open source scientific computing community. If you like
 Xarray and want to support our mission, please consider making a donation_
 to support our efforts.
 
-.. _donation: https://www.flipcause.com/secure/cause_pdetails/NDE2NTU=
+.. _donation: https://numfocus.salsalabs.org/donate-to-xarray/
 
 
 History