Revert "Bring back "Updates to preview modal for release""

src/components/gui/gui.jsx

src/components/import-modal/import-modal.css

src/components/import-modal/import-modal.jsx

src/components/preview-modal/preview-modal.css

src/components/preview-modal/preview-modal.jsx

src/containers/gui.jsx

src/containers/import-modal.jsx

src/containers/preview-modal.jsx

src/reducers/modals.js

test/integration/project-loading.test.js