ci: use master seL4

Signed-off-by: Bill Nguyen <bill.nguyen@student.unsw.edu.au>

Author: dreamliner787-9

.github/workflows/sdk.yaml

@@ -29,7 +29,7 @@ jobs:
         uses: actions/checkout@v4
         with:
             repository: seL4/seL4
-            ref: microkit
+            ref: master
             path: seL4
       - name: Install SDK dependencies
         run: |