Fix changelog URL in 7.0.0rc1 announcement (#9379)

The-Compiler · web-flow · commit 5cb50fa13cfc · 2021-12-07T10:04:55.000Z
The changelog does not exist at /stable because an rc isn't stable...
diff --git a/doc/en/announce/release-7.0.0rc1.rst b/doc/en/announce/release-7.0.0rc1.rst
@@ -19,7 +19,7 @@ You can upgrade from PyPI via:
 
 Users are encouraged to take a look at the CHANGELOG carefully:
 
-    https://docs.pytest.org/en/stable/changelog.html
+    https://docs.pytest.org/en/7.0.x/changelog.html
 
 Thanks to all the contributors to this release:
 
