<tr>
    {{#if hasBlock}}
        {{yield header}}
    {{else}}
        {{#each columnKeys as |column| }}
            {{simple-table-cell header=header dataKey=column }}
        {{/each}}
    {{/if}}
</tr>

{{#if hasBlock}}
    {{yield header}}
{{else}}
    <tr>
        {{#each columnKeys as |column| }}
            {{simple-table-cell header=header dataKey=column }}
        {{/each}}
    </tr>
{{/if}}

Remove tr tag from header yield
Remove tr tag from header yield
