fix(deps): pin dependencies (#541)

Author: renovate-bot

package.json

@@ -61,7 +61,7 @@
     "karma-coverage-istanbul-reporter": "3.0.3",
     "karma-mocha": "2.0.1",
     "karma-spec-reporter": "0.0.32",
-    "karma-webpack": "^4.0.2",
+    "karma-webpack": "4.0.2",
     "mocha": "7.2.0",
     "nyc": "15.1.0",
     "rimraf": "3.0.2",