Skip comments in remove_pre_ampersands

[max-models]

This PR resolves a problem when trying to use fprettify on continued lines with comments in between. Mentioned here.

For example, the following code

program mwe_bad_line_continuation
   implicit none

   real :: x, y, z

   x = 1.0
   y = 2.0

   z = x + &
       ! comment
        & y
   print *, z
end program mwe_bad_line_continuation

previously gave raise FprettifyParseException("Bad continuation line format", filename, line_nr) error.