GitHub: update litd itest branch

We need to update the way we assert balances in the integration tests,
because with the changes in this PR we no longer show channel funding
related asset outputs by default.

Author: guggero

.github/workflows/main.yaml

@@ -21,7 +21,7 @@ env:
 
   GO_VERSION: '1.23.6'
 
-  LITD_ITEST_BRANCH: 'master'
+  LITD_ITEST_BRANCH: 'script-key-migrations'
 
 jobs:
   #######################