itch automatically adds pixiJS on the made with tag on my game, how does itch knows which engine i use and how do i remove them?

I don't think Itch.io automatically know show you made it - but it can be triggered by a keyword that you selected.

Go to your game - At the top there are tabs - Edit - DevLog  - Metadata.

Select Metadata - on the side select: Engines and Tools.  Change or delete it there.

i checked it already, the game engine is  generated automatically even when i left it blank.

So... which game is this? You have half a dozen.

I'm not aware of any automatic detection. You might want to contact support and ask.