Remove Autotools Cygwin PR action (#5031)

Author: derobins

.github/workflows/autotools.yml

@@ -90,12 +90,6 @@ jobs:
       with:
             build_mode: "production"
 
-    call-release-auto-cygwin:
-      name: "Autotools Cygwin Workflows"
-      uses: ./.github/workflows/cygwin-auto.yml
-      with:
-            build_mode: "production"
-
     call-release-auto-xpr:
         name: "Autotools TestExpress Workflows"
         uses: ./.github/workflows/testxpr-auto.yml