Fix remove !important on CSS variable declarations

[RobinMalfait]

This PR fixes an issue where !important is added to declarations that define CSS variables. The !important should only be added to the other declarations.

Before:

.ease-out\! {
  --tw-ease: var(--ease-out) !important;
  transition-timing-function: var(--ease-out) !important;
}

After:

.ease-out\! {
  --tw-ease: var(--ease-out);
  transition-timing-function: var(--ease-out) !important;
}

Fixes: #16664