fix CI badge (#13003)

Author: reaperhulk

README.rst

@@ -9,9 +9,8 @@ pyca/cryptography
     :target: https://cryptography.io
     :alt: Latest Docs
 
-.. image:: https://github.com/pyca/cryptography/workflows/CI/badge.svg?branch=main
-    :target: https://github.com/pyca/cryptography/actions?query=workflow%3ACI+branch%3Amain
-
+.. image:: https://github.com/pyca/cryptography/actions/workflows/ci.yml/badge.svg
+    :target: https://github.com/pyca/cryptography/actions/workflows/ci.yml?query=branch%3Amain
 
 ``cryptography`` is a package which provides cryptographic recipes and
 primitives to Python developers. Our goal is for it to be your "cryptographic