chore: fix small todo

Author: alfetopito

apps/cowswap-frontend/src/cosmos.decorator.tsx

@@ -37,9 +37,7 @@ const DarkModeToggleButton = styled.button`
   padding: 6px 10px;
 `
 
-// TODO: Add proper return type annotation
-// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
-const DarkModeToggle = ({ children }: { children?: ReactNode }) => {
+const DarkModeToggle = ({ children }: { children?: ReactNode }): ReactNode => {
   const theme = useContext(ThemeContext)
   const [darkMode, toggleDarkModeAux] = useDarkModeManager()
   const toggleDarkMode = useCallback(() => {