GitHub: use lnd-19-2 branch for litd itest

Author: guggero

.github/workflows/main.yaml

@@ -21,7 +21,7 @@ env:
 
   GO_VERSION: '1.23.9'
 
-  LITD_ITEST_BRANCH: 'master'
+  LITD_ITEST_BRANCH: 'lnd-19-2'
 
 jobs:
   #######################