chore(deps): update dependency @sourcegraph/tsconfig to v4

Author: renovate-bot

package.json

@@ -101,7 +101,7 @@
     "@commitlint/cli": "^7.0.0",
     "@commitlint/config-conventional": "^7.0.1",
     "@sourcegraph/prettierrc": "^2.2.0",
-    "@sourcegraph/tsconfig": "^3.0.0",
+    "@sourcegraph/tsconfig": "^4.0.0",
     "@sourcegraph/tslint-config": "^12.3.1",
     "@types/mocha": "5.2.5",
     "@types/node": "10.12.18",

yarn.lock

@@ -853,10 +853,10 @@
   resolved "https://registry.yarnpkg.com/@sourcegraph/prettierrc/-/prettierrc-2.2.0.tgz#af4a6fcd465b0a39a07ffbd8f2d3414d01e603e8"
   integrity sha512-kRdHxdAppxYnN7qAQjNTyuG05pjYHFtEUquZauXVXBeaGB4sye3uSkb8wgi34jeaUHG/gWp2f5hQgCCBMizjjA==
 
-"@sourcegraph/tsconfig@^3.0.0":
-  version "3.0.0"
-  resolved "https://registry.yarnpkg.com/@sourcegraph/tsconfig/-/tsconfig-3.0.0.tgz#dfd8a0072d55a219118f58cfbca71336b58991b2"
-  integrity sha512-/2Q4lAQvHPGkddV7+4FRBgJPIzWw0e364kYq3IkD22H9eHJdA0KHfKXAKmWQjbtVpWSQeNPyVJ1pT5emfef4TQ==
+"@sourcegraph/tsconfig@^4.0.0":
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/@sourcegraph/tsconfig/-/tsconfig-4.0.0.tgz#dd2a406f90760bb789fd89fde4bd0a8d681f2767"
+  integrity sha512-jxrhKbek4yu1HUDpUhqR9hAGFiUgaJ9NIM+c8JEkAnvpW67ab1AUFWb82aSVfZWX1UVqfR84AMr7xP3E8LlL+A==
 
 "@sourcegraph/tslint-config@^12.3.1":
   version "12.3.1"