Fix broken React component import: `RegionFilter`

[kachkaev]

From Netlify build:

10:01:08 PM: warn  - Compiled with warnings
10:01:08 PM: ./src/components/inherited-map/components/filter-panel/filter-panel-normal.js
10:01:08 PM: Attempted import error: 'RegionFilter' is not exported from './region-filter' (imported as 'RegionFilter').
10:01:08 PM: Import trace for requested module:
10:01:08 PM: ./src/components/inherited-map/components/filter-panel/filter-panel.js
10:01:08 PM: ./src/components/inherited-map/components/filter-panel/index.ts
10:01:08 PM: ./src/components/inherited-map/inherited-map.tsx
10:01:08 PM: ./src/components/inherited-map/index.ts
10:01:08 PM: ./src/pages/iframes/map.tsx

This was not covered by linting because we use .js instead of .ts here. Prod should not be affected because we don't seem to filter by region. Might be a good idea to convert all inherited files to ts.

[alexander-mart]

category-header.js
date-filter.js
filter-panel-category.js
filter-panel-hidden.js
filter-panel-normal.js
filter-panel.js

From: https://github.com/dtpstat/website/tree/main/src/components/inherited-map/components/filter-panel