Probably but it doesn't matter
I would assume they don't know that he is still alive as that would seem contradictory to him wanting to keep a few things secret (for example, his wife). Per the Avengers side of things, they seem pretty fragmented in Far From Home but they too would probably want to keep it a secret out of respect for Steve.
The fact that he is in the video points to the fact that the public almost certainly don't know he is still alive and think he died in the Battle for Earth.
However, it doesn't matter if he died or became too old, he is still no longer an Avenger and the video is commemorating those Avengers that saved the world that are "no longer with us". For all intents and purposes death and being too old to be of much help are pretty synonymous in the world of being a superhero.
It's also worth pointing out that Far From Home takes places 8 months after Endgame and so Steve could have died in that time. I highly doubt he has but he's an old man so it is a possibility.