How do I remove the classes from the pager item-list in Drupal 7?
To override the markup of the pager, override the theme_pager() theme function.

However in your case you want to override the class in the item list so for that you need to also override theme_item_list().

For information on overriding theme functions see the beginners guide to overriding themeable output, and for more thorough drupal themeing information see themeing drupal 6 and 7