ensure modifiers are unique

For the `mask-*` utilities, we do call `suggest(…)` multiple times, so
there could be some duplication. The `modifiers` are a simple array and
not a Set so let's make them unique here.

Ideally we don't call suggest with the same values, but that requires a
bigger internal refactor.

Another ideal situation would be if `modifiers` was a Set in the first
place. But since it's export and "public" API I didn't want to change
that datastructure.

Author: RobinMalfait

packages/tailwindcss/src/intellisense.ts

@@ -55,6 +55,9 @@ export function getClassList(design: DesignSystem): ClassEntry[] {
           item.fraction ||= fraction
           item.modifiers.push(...group.modifiers)
         }
+
+        // Deduplicate modifiers
+        item.modifiers = Array.from(new Set(item.modifiers))
       }
     }
   }