Fix invalid file seek in the file containing CRLF

In the file containing CRLF, below code gets unexpected results.
```ruby
file.each_line {|line|
  p "pos=#{file.seek}, bytesize=#{line.bytesize}"
  # => pos=69, bytesize=68
  # => expected results = pos=68, bytesize=68
}
```

In the file containing only LF, upper code gets expected results.
So I removed the code for computing `seek` from `file.pos` and `line.bytesize`.