It is always Newton because it is inevitable. You learned about Gravity from Newton and even if you don't do time-travel and explain gravity to him, he will end up discovering it in one way or the other and the "kiddo you" (your original timeline's past self) would be learning about it in the future (your past).
Let's say Newton discovered Gravity on 26th July 1675 and you travelled to 25th July 1675 and explained Gravity to him and came back to the present, it won't change anything, it still won't change the fact that you learned about Gravity from Newton in the first place. Although you time-travelled and taught Newton about Gravity, that didn't change the origin story, you just preponed the event and saved Newton a lot of time.
That still didn't change the fact that Newton discovered it, It was still Newton, he would explain the world about Gravity just one day earlier, he would publish the work one day earlier in his name, then the "kiddo you" (now your original timeline's past's new future kiddo version) would be reading "Newton discovered Gravity" in the future (altered but not so altered future).
So it is Newton by all accounts. You can't change or challenge the inevitable (this inevitable is created by you, you made sure of it by travelling in time, you just preponed an event).
Am I making sense?