Fixed a grammar error in topics/i18n/translation.

Overview

========

In order to make a Django project translatable, you have to add a minimal amount

of hooks to your Python code and templates. These hooks are called

In order to make a Django project translatable, you have to add a minimal

number of hooks to your Python code and templates. These hooks are called

:term:`translation strings <translation string>`. They tell Django: "This text

should be translated into the end user's language, if a translation for this

text is available in that language." It's your responsibility to mark