[lldb] Prevent dwim-print from showing kNoResult error

Expression evaluation for `void` valued expressions sets an error using the `kNoResult`
code. Like the `expression` command, `dwim-print` should also not print such errors.

Before:

```
(lldb) dwim-print (void)printf("hi\n")
hi
Error: 'unknown error'
```

After:

```
(lldb) dwim-print (void)printf("hi\n")
hi
```

rdar://109746544

Differential Revision: https://reviews.llvm.org/D151351