Fix submit row text being slightly too far left.

I noticed that the text on the submit button was slight left of centre.

So I removed the use of #field_buffer. I tried this on multiple devices in the simulator and all appeared to still be centred after the fix was in place.

Here is a before and after shot:

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### Before (with #field_buffer)

![screen shot 2013-11-07 at 7 36 46 am](https://f.cloud.github.com/assets/94960/1486499/72f03580-4724-11e3-9e50-2d6cad37635f.png)

### After (without #field_bufder)

![screen shot 2013-11-07 at 7 38 41 am](https://f.cloud.github.com/assets/94960/1486500/75635e0a-4724-11e3-8052-5ddb948d9c3c.png)