Edit with new information from an authoritative source:
The show writers weighed in on Twitter saying there will not be any content edits, even denying the potential retroactive edit of Will's birthday. The edit I mentioned below of Jonathan's photo-taking in S1E2 was apparently a Tiktok hoax.
Original (wrong) answer:
I just came across an article saying they removed part of the scene in Season 1 where Jonathan Byers takes pictures of Nancy undressing at Steve's house after the pool party. The photo he took still appears in a later episode where Steve and his friends confront Jonathan for being creepy and break his camera.
This theory showed up in June 2022, and it says in the first episode of Season 1 when Will was heading home and crashed his bike there were Vecna-style grandfather clock chimes. I haven't been able to verify by comparing with the blu-rays.
I haven't seen any others yet but I have been following Stranger Things articles closely looking for any other announcements.