Hi.When a personal subject is the focus, we can use who instead of that. We often omit who in informal situations when it is the object of the verb:
It was my husband who (or that) you spoke to on the phone. (or It was my husband you spoke to on the phone.)
It was in June we got married Source : Cambridge Dictionary
According to Cambridge Dictionary, it seems that when the focus of a cleft sentence is the object of the verb, we can omit who or that.
Then, how can I explain the title of the internet site, 'It was in june we got married'? 'In june' isn't the object of 'got married'.