Typo error : key template is missing

Typo error : `key` template is missing

```
{{ sonata_block_render({ 'type': 'sonata.block.service.template' }, {
    'MyMenuBundle:Block:menu.twig.html'
}) }} 
```

must be 
```
{{ sonata_block_render({ 'type': 'sonata.block.service.template' }, {
    'template':'MyMenuBundle:Block:menu.twig.html'
}) }} 
```