chore(deps): update dependency @sourcegraph/tslint-config to v12 (sourcegraph#509)

Author: renovate[bot]

package-lock.json

@@ -66,7 +66,7 @@
   "devDependencies": {
     "@sourcegraph/prettierrc": "^2.2.0",
     "@sourcegraph/tsconfig": "^3.0.0",
-    "@sourcegraph/tslint-config": "^11.1.1",
+    "@sourcegraph/tslint-config": "^12.0.0",
     "@types/chai": "4.0.6",
     "@types/chai-as-promised": "7.1.0",
     "@types/glob": "5.0.35",