the formula you would want is

=regexreplace("cell with your data","\n","")  

or

=regexreplace("cell with your data","\r","")

the first one replaces new lines and the second on replaces carriage returns if needed.

the formula you would want is

=regexreplace("cell with your data","(\n)(\n{1,})","$1")

or

=regexreplace("cell with your data","(\r)(\r{1,})","$1")

the first one replaces new lines and the second on replaces carriage returns if needed.