Fix table in "Data format (en).md"
Fix table in "Data format (en).md"

The markdown formatting of the "Properties" example table in the English data format documentation was broken, at least on GitHub. I took the opportunity to fully align the table columns in the markdown source, but that is not necessary, as you only need to add a pipe at the start of each row which starts with an empty cell.
Artsdatabanken/identification_key,Artsdatabanken/identification_key,Artsdatabanken/identification_key,Artsdatabanken/identification_key,Artsdatabanken/identification_key,Artsdatabanken/identification_key,Artsdatabanken/identification_key