chore: remove a deprecated webpack flag

as webpack-cli starts to complain about those from v4.

package.json

@@ -176,7 +176,7 @@
   },
   "scripts": {
     "analyzebundle": "NODE_ENV=production webpack --config ./webpack/webpack.analyze.js",
-    "build:assets": "npm run clean && lingui compile && NODE_ENV=production webpack --colors --config ./webpack/webpack.production.js",
+    "build:assets": "npm run clean && lingui compile && NODE_ENV=production webpack --config ./webpack/webpack.production.js",
     "build:validate": "scripts/validate-build dist/assets/*.js",
     "build": "npm run build:assets && npm run build:validate",
     "build-release-bump": "./scripts/build-release-bump.sh",
@@ -193,8 +193,8 @@
     "prestart": "npm run util:env:validate",
     "pretty-quick": "pretty-quick",
     "release": "semantic-release",
-    "start:testing": "NODE_ENV=testing webpack-dev-server --config ./webpack/webpack.dev.js --hot --progress --colors --content-base ./dist --host 0.0.0.0 --port $npm_package_config_port",
-    "start": "lingui compile && NODE_ENV=development webpack-dev-server --config ./webpack/webpack.dev.js --hot --progress --colors --content-base ./dist --host 0.0.0.0 --port $npm_package_config_port",
+    "start:testing": "NODE_ENV=testing webpack-dev-server --config ./webpack/webpack.dev.js --hot --progress --content-base ./dist --host 0.0.0.0 --port $npm_package_config_port",
+    "start": "lingui compile && NODE_ENV=development webpack-dev-server --config ./webpack/webpack.dev.js --hot --progress --content-base ./dist --host 0.0.0.0 --port $npm_package_config_port",
     "test:integration:local": "cypress open",
     "test:integration": "./scripts/run-integration-tests",
     "test:system": "./scripts/run-system-tests",