Remove extra • separator before empty game metadata fields

[Keltena]

Entry listings on /ballot and /comp include a bullet after each metadata field. This works as long as the last field (platform) isn't blank:

Horror • Half an hour • Web-based

However, the platform field is left blank if set to "Other", which results in dangling separators:

Fantasy • Two hours •

This pull request tweaks the template to print separators only between two non-empty fields.

(A simpler fix would be to just print "Other", but I'm assuming that decision was made for a reason.)

[coveralls]

coverage: 63.298%. remained the same
when pulling a9f70e0 on Keltena:entry-metadata-display
into de7eb0e on iftechfoundation:main.