Markup in the Contributing docs for prop and vars tables needs to be updated

[blazebarsamian]

I'm submitting a ...

• bug report
• feature request
• support request

What is the current behavior?
Currently in the contributing doc the markup used for the example prop and vars tables is old. The HeadStacked portion has been updated in the table component since then and now needs to be updated in the contributing doc.

Currently written like this:

<Table.HeadStacked>
  <Table.Data>[ComponentName] Props</Table.Data>
</Table.HeadStacked>

What is the expected behavior?
HeadStacked should be written like this:

<Table.HeadStacked>
  <Table.Row>
    <Table.Header>[ComponentName] Props</Table.Header>
  </Table.Row>
</Table.HeadStacked>

For feature requests: why should the behavior change?

because it wont properly work the way its written and people are using that as a guide for writing their prop and var tables.