Twenty Twelve: Standardize label used for Web Fonts option

[jkudish]

The label for enabling the Open Sans web font in the theme is different in the theme options and in the theme customizer page. In the theme options page, it's labelled: "Yes, I'd like to enable the gorgeous, open-source <em>Open Sans</em> typeface." whereas in the customizer it's labelled "Enable Web Fonts". The customizer label is confusing as it makes it sound like there is more than one web font to choose from and generally sounds like a different option from the one presented in the theme options page.

The proposed page changes the label in the customizer to match the one in the options page.

Looks good. +1

In [21448]:

Twenty Twelve: standardize label used for Web Fonts option. Props jkudish, fixes #21487.