Fix GPG key note in README

README.rst

@@ -93,10 +93,11 @@ Installations are tested on CPython and PyPy implementations.
     pip install xdoctest
 
 
-Distributions on pypi are signed with a GPG public key: ``D297D757``. If you
-care enough to check the gpg signature (hopefully pip will just do this in the
-future), you should also verify this agrees with the contents of
-``dev/public_gpg_key``.
+
+Github releases are signed with a GPG public key: ``59A34380`` (note: this
+incorrectly was listed as ``D297D757`` for before 2024-11-15, which was an
+older CI signing key). If you care enough to check the gpg signature, you
+should also verify this agrees with the contents of ``dev/public_gpg_key``.
 
 
 Usage: run your doctests