fix: remove unused variables from catalog and post views

- catalog.tsx: Remove unused 'coloredFeed' variable assignment in useMemo
- post.tsx: Remove unused 'useState' import

The useMemo in catalog.tsx still executes its side effects (applying filter
colors to the store) without needing to assign the return value.

src/views/post/post.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react';
+import { useEffect } from 'react';
 import { useTranslation } from 'react-i18next';
 import { Comment, Role, useComment, useEditedComment, useSubplebbit } from '@plebbit/plebbit-react-hooks';
 import useSubplebbitsStore from '@plebbit/plebbit-react-hooks/dist/stores/subplebbits';