ignore ShellCheck warning

`calculate_move()` must be overwritten by a client implementation.  In
the 'include file' `bash-n-client`, ShellCheck correctly notes that
the `_die()` call in the boilerplate `calculate_move()` implementation
will make subsequent code unreachable.  But in this case that works as
designed, so just ignore the note.

```
./bash-n-client:103:5: note: Command appears to be unreachable. Check usage (or ignore if invoked indirectly). [SC2317]
```

bash-n-client

@@ -100,6 +100,7 @@ _on_execute_turn()
 {
     local hash=$1
     calculate_move
+    # shellcheck disable=SC2317
     _send INSERT $? "$hash"
 }