Try to fix blog module confusion by proper module description

It is an often stated problem, that people confuse blog module as something to keep their own single user blogs in. Most Drupal experts would have told them to use stories (pre Drupal 5.0) to maintain a single man blog however. Now while translating the description strings, I found that the blog.info file might be one of the confusion factors. It does tell that the module's feature is to provide *one* *blog*, and not multiple *user* *blogs*.

This is just a very simple wording patch.