This is not the same syntax as the one I used, so simply removing it will be a breaking change. I don't think I have a lot of websites using this syntax so I could go with a minor update (so that renovate will catch it).
I think the only one using it are:
Sov, for the progressbar but it will get revamped anyway
Monsters and Society, I think they use this for adding smoother semi-transparent layer on the sidebar and header shadow
This has been integrated into the core for a few minor versions already: https://github.com/tailwindlabs/tailwindcss/pull/2176
This is not the same syntax as the one I used, so simply removing it will be a breaking change. I don't think I have a lot of websites using this syntax so I could go with a minor update (so that renovate will catch it).
I think the only one using it are: