It won't poison the soil, but in time (given that yew is very slow growing) it will cut out the light to your border, depending of course which direction you face, and the roots will take moisture and nutrients from the soil, so your plants/shrubs will suffer.

Don't forget, as well, that every part of the yew is poisonous so if you had young children in your garden who might eat the bright berries, that might be a problem in the future - but not for a long time.

The arils (the red fleshy parts that swell up and surround the seed) are very sweet but safe to eat (we've eaten them only after learning so) and are I understand the only part that is not poisonous.
Although one would tell children not to eat yew at all, to stay safe. And make sure that you don't eat the seed inside if you try an aril .......

I learned that, too, Longleaf - Henry (our Lab.) hoovered up a whole lot of berries along the lane - and the vet wanted to be sure he hadn't chewed them because of the seed. Labs don't chew berries - they're so greedy - luckily.