don't fallback to exiftool for embedded image previews (#2747)

Given #2668 introduced support for imagemagick and libraw, this should no
longer be necessary which allow for reduced code footprint and complexity.

Fixes: #2744

server/test/repositories/media.repository.mock.ts

@@ -2,7 +2,6 @@ import { IMediaRepository } from '@app/domain';
 
 export const newMediaRepositoryMock = (): jest.Mocked<IMediaRepository> => {
   return {
-    extractThumbnailFromExif: jest.fn(),
     extractVideoThumbnail: jest.fn(),
     resize: jest.fn(),
     crop: jest.fn(),