Translation fix in studio: For better translation in unit.html

As the sentence in unit.html is splitted into three parts due to the varible release_date may be None, it breaks the integrity of a sentence.
Different language may have different word or event grammer order, so if a sentence is breaked into three parts, translators cannot adjust the word orders to create a good translation.
This fix tries to combine the sentence together so that translators can freely change the orders of sentence parts to make a good translation.