Thank you, Kenneth, got the solution with your help:
I see the syntax of Regex on DW is different than BBEdit.
But seems to be a bug of Dreamweaver because "$ (dollar)" must do the work instead of using \n.
Check the concept of $ (dollar):
$ (dollar): Matches at the end of the string the regex pattern is applied to. Matches a position rather than a character. Most regex flavors have an option to make the dollar match before line breaks (i.e. at the end of a line in a file) as well. Also matches before the very last line break if the string ends with a line break.