[UI] Remove theme constants from twenty-front and use the ones exported from twenty-ui. (#5558)

Some parts of the Frontend used theme constants exported from
`modules/ui` while other parts used theme constants exported from
`twenty-ui`.

This PR centralizes theme constants by removing them from `modules/ui`
completely.

packages/twenty-front/src/modules/activities/components/CustomResolverFetchMoreLoader.tsx

@@ -1,7 +1,6 @@
 import { useInView } from 'react-intersection-observer';
 import styled from '@emotion/styled';
-
-import { GRAY_SCALE } from '@/ui/theme/constants/GrayScale';
+import { GRAY_SCALE } from 'twenty-ui';
 
 type FetchMoreLoaderProps = {
   loading: boolean;