Description
There is an extra bottom border under the last <th> (row header) in the table. It makes the table look weird.
I changed the CSS so the last row header (<th scope="row">) does not show a bottom border.

Type of change:

• Bug fix
• New feature
• Other

Code sample to show the issue:

<MudSimpleTable Dense Elevation="0">
    <tbody>

    <tr>
        <th scope="row">Row Header A</th>
        <td>Something</td>
    </tr>

    <tr>
        <th scope="row">Row Header B</th>
        <td>Something Else</td>
    </tr>

    <tr>
        <th scope="row">Row Header C</th>
        <td>Something Something</td>
    </tr>
    </tbody>
</MudSimpleTable>

Before:

After:

Checklist:

• The PR is submitted to the correct branch (dev)
• My code follows the code style of this project
• I've added relevant tests