Correct indenting in ePBL_column

  Corrected the indenting in most of the lines of ePBL_column to respect the
MOM6 2-space indenting convention, and eliminated the comment explaining why the
incorrect indenting had previously been retained to facilitate the review of a
pull request with substantial actual changes in this routine.  Apart from a
single comment that was removed, only white space is changed, and all answers
are bitwise identical.