Add setup file to integration test (#12855)

tests/integration/__tests__/plugin-options-string.js

@@ -1,6 +1,4 @@
 import snapshotDiff from "snapshot-diff";
-import runPrettier from "../run-prettier.js";
-
 test("show external options with `--help`", async () => {
   const originalStdout = await runPrettier("plugins/options-string", ["--help"])
     .stdout;