Remove useless 'delete overviews' message.

The message was useless because it was being emitted for every sync update
regardless of whether overviews existed or not. And it was flooding Rollbar.

services/importer/lib/importer/overviews.rb

@@ -60,7 +60,6 @@ module CartoDB
       end
 
       def delete_overviews!(table_name)
-        CartoDB::Logger.info message: "Deleting overviews", user: @user, table_name: table_name
         @user.transaction_with_timeout statement_timeout: @statement_timeout do |db|
           log("Will delete overviews for #{table_name}")
           Carto::OverviewsService.new(db).delete_overviews(table_name)