Change mapping of DC Coverage from <temporal> to <topic>

According to the CUL specs, the DC Coverage field should be mapped
to <subject<temporal>. However, in the remediated metadata, this field
often contains geographical information. Furthermore, the example in
the CUL specs uses <subject><topic>. So, for now, the mapping was
changed to <subject><topic>
Regenerate MODS due to change in DC Coverage mapping