Update ci_shellcheck.yml: go 3 levels

.github/workflows/ci_shellcheck.yml

@@ -27,7 +27,7 @@ jobs:
         run: |
           # check bash files (bash -n, shellcheck -x)
           err=0
-          for i in $(find . -maxdepth 2 -name '*.sh'); do
+          for i in $(find . -maxdepth 3 -name '*.sh'); do
             echo "==================== $i"
             bash -n $i
             if [ $? -ne 0 ]; then