Revert "Bump test from 1.26.3 to 1.28.0 in /cipd_packages/codesign (#4887)"

This reverts commit 7d7ac6c.

Author: ievdokdm

cipd_packages/codesign/pubspec.yaml

@@ -22,4 +22,4 @@ dependencies:
 dev_dependencies:
   dart_flutter_team_lints: 3.5.1
   lints: 5.0.0
-  test: 1.28.0
+  test: 1.26.3