chore(deps): update dependency karma to v6

Author: renovate-bot

package.json

@@ -44,7 +44,7 @@
     "@sourcegraph/prettierrc": "^3.0.3",
     "@sourcegraph/tsconfig": "^4.0.1",
     "@types/chai": "4.2.14",
-    "@types/karma": "5.0.1",
+    "@types/karma": "6.3.1",
     "@types/karma-webpack": "2.0.9",
     "@types/lodash": "4.14.170",
     "@types/mocha": "8.2.2",
@@ -58,7 +58,7 @@
     "esm": "^3.2.25",
     "husky": "^4.3.5",
     "istanbul-instrumenter-loader": "^3.0.1",
-    "karma": "^5.2.3",
+    "karma": "^6.3.6",
     "karma-chai": "^0.1.0",
     "karma-chrome-launcher": "^3.1.0",
     "karma-coverage-istanbul-reporter": "^3.0.3",