If you are using the Russian keyboard, it's the new default (since iOS 11). Before that, you had to long-press the " to get it (along with ˝, „ and all these other marks.

Interestingly, the computer keyboards are stuck with the old layouts. You can't buy a Russian keyboard with the right quotation marks. I am using a custom layout by Ilya Birman [1] that makes a nice remapping with «» available quickly.

[1] https://ilyabirman.ru/projects/typography-layout/