Fix rust_doctests

Author: antoyo

.github/workflows/ci.yaml

@@ -231,7 +231,7 @@ jobs:
           grep '] rust_print: Info message (level 6) with args$'         qemu-stdout
           grep '] rust_print: A line that is continued with args$'       qemu-stdout
 
-      - run: grep '] ok 2 rust_doctests_kernel$' qemu-stdout
+      - run: grep '] ok 4 rust_doctests_kernel$' qemu-stdout
 
       - run: python ci/check_panics.py qemu-stdout