Tidy devDeps, all the webpack stuff lives in the layer above

package.json

@@ -149,7 +149,6 @@
     "eslint-plugin-flowtype": "^2.50.3",
     "eslint-plugin-react": "^7.20.3",
     "eslint-plugin-react-hooks": "^2.5.1",
-    "file-loader": "^3.0.1",
     "glob": "^5.0.15",
     "jest": "^24.9.0",
     "jest-canvas-mock": "^2.2.0",
@@ -158,7 +157,6 @@
     "matrix-react-test-utils": "^0.2.2",
     "react-test-renderer": "^16.13.1",
     "rimraf": "^2.7.1",
-    "source-map-loader": "^0.2.4",
     "stylelint": "^9.10.1",
     "stylelint-config-standard": "^18.3.0",
     "stylelint-scss": "^3.18.0",