Remove test for `write_scen_file` output
Remove test for `write_scen_file` output

The previously added test output includes timestamp which makes
comparing the output depend on happening in the same minute.
Example:
    E             - 12-22 13:35
    E             ?           ^
    E             + 12-22 13:36
    E             ?

openclimatedata/pymagicc,openclimatedata/pymagicc