Finder Frontend: Increase shm_size

This fixes out of memory issues with running the Cucumber test suite
through GOV.UK Docker by increasing shared memory size in line with some
of the publishing apps.

projects/finder-frontend/docker-compose.yml

@@ -8,6 +8,7 @@ x-finder-frontend: &finder-frontend
     dockerfile: Dockerfile.govuk-base
   image: finder-frontend
   stdin_open: true
+  shm_size: 512mb
   tty: true
   volumes:
     - ${GOVUK_ROOT_DIR:-~/govuk}:/govuk:delegated