Bug: Virtual rule empty-table-header should pass with a table role if none

This failing the needs to be added and resolved:

```
it('should pass with a table of role none', function () {
var table = new axe.SerialVirtualNode({
nodeName: 'table',
attributes: {
role: 'none'
}
});

var tr = new axe.SerialVirtualNode({
nodeName: 'tr',
});

var th = new axe.SerialVirtualNode({
nodeName: 'th',
});

tr.children = [th];
tr.parent = table;
th.parent = tr;
th.children = [];
table.children = [tr];

var results = axe.runVirtualRule('empty-table-header', table);

assert.lengthOf(results.passes, 1);
assert.lengthOf(results.violations, 0);
assert.lengthOf(results.incomplete, 0);
});
```

__Originally posted by @dbowling in https://github.com/dequelabs/axe-core/pull/3801#discussion_r1041268076__

Start with the empty-table-header virtual rule and the supplied runVirtualRule test case. Add the shown table-role-none scenario, then run the relevant virtual-rule tests; done means it reports one pass with no violations or incomplete results.

Written by the indexing model from the issue text.