Refine color validator test typing

Co-authored-by: sawka <2722291+sawka@users.noreply.github.com>

Author: Copilot

frontend/util/color-validator.test.ts

@@ -36,7 +36,7 @@ describe("validateCssColor", () => {
     });
 
     it("throws for invalid CSS colors", () => {
-        expect(() => validateCssColor(":not-a-color:" as any)).toThrow("Invalid CSS color");
+        expect(() => validateCssColor(":not-a-color:")).toThrow("Invalid CSS color");
         expect(() => validateCssColor("#12")).toThrow("Invalid CSS color");
         expect(() => validateCssColor("rgb(255, 0)")).toThrow("Invalid CSS color");
     });