Use non-deprecated windows nightly label

Author: josephnoir

.github/workflows/main.yml

@@ -69,5 +69,5 @@ jobs:
     with:
       windows_6_0_enabled: true
       windows_6_1_enabled: true
-      windows_nightly_6_1_enabled: true
+      windows_nightly_next_enabled: true
       windows_nightly_main_enabled: true

.github/workflows/pull_request.yml

@@ -73,5 +73,5 @@ jobs:
     with:
       windows_6_0_enabled: true
       windows_6_1_enabled: true
-      windows_nightly_6_1_enabled: true
+      windows_nightly_next_enabled: true
       windows_nightly_main_enabled: true