Prevent WP from wrapping html in caption shortcode after ‘image_send_editor’ filter is applied

You can use the disable_captions filter, Just put it in your functions.php

add_filter( 'disable_captions', create_function('$a', 'return true;') );

Edit: As toscho pointed out this is a better solution!

add_filter( 'disable_captions', '__return_true' );