I would experiment on a sample and use a python expression emulating the following
a = "a line \n with another line"
print(a)
a line
with another line
b = a.replace("\\","")
print(b)
a line
with another line
this could be done in the field calculator as a simple expression with the python parser
!YourField!.replace("\\", "")
did I mention a sample, test file