Invalid minification of CSS decalaration using sibling-index() #4515

Minifying a CSS declaration where sibling-index() is multiplied by a value with a unit can result in an invalid declaration.

For example: animation-delay: calc(sibling-index() * 0.05s); minifies to animation-delay:calc(sibling-index()/20s), which is invalid because the numerator is unitless and the denominator has a unit.

Minimal test case:

1. create a css file with this content or clone this repo

div {
  animation-delay: calc(sibling-index() * 0.05s);
}

2. run esbuild --bundle {css filename} --minify --outfile=out.css or npm run build in the test repo
3. out.css includes the invalid css value