I think all the numbers are for all of Palestine - the population, the number of journalist fatalities, and the number of total deaths (most would be in Gaza, but the IDF is apparently also continuing activities in the West Bank which are killing Palestinians and included in the total - see for example https://www.ohchr.org/en/press-briefing-notes/2023/11/alarming-urgent-situation-occupied-west-bank-including-east-jerusalem).

If I had separated out numbers, focusing on the Gaza subset would probably tell a similar story; it might remove some noise that could have masked a significant difference in proportions if the difference was more marginal. However, including the whole of Palestine the proportion difference was still extremely highly significant - there can be no doubt from the numbers that journalists in Palestine are more likely to be killed than any random citizen.