backout whatsnew update

Author: bjlittle

docs/src/whatsnew/latest.rst

@@ -288,9 +288,6 @@ This document explains the changes made to Iris for this release
 #. `@wjbenfold`_ fixed tests for hybrid formulae that weren't being found by
    nose (:issue:`4431`, :pull:`4450`)
 
-#. `@bjlittle`_ adopted GitHub Actions for continuous integration.
-   (:pull:`4503`)
-
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,
     core dev names are automatically included by the common_links.inc: