Specify snapshotFormat in jest.config.js for integration tests

Jest 29 changed the default snapshot format (see
https://github.com/facebook/jest/blob/94c06ef0aa9b327f3c400610b861e7308b29ee0d/docs/UpgradingToJest29.md).
To maintain compatibility with prior versions, we preserve the old snapshot
format rather than update the snapshots to the new format.

Author: ramosbugs

packages/jest-plugin/test/integration-input/jest.config.js

@@ -8,6 +8,13 @@ module.exports = {
   reporters: ["@unflakable/jest-plugin/dist/reporter"],
   runner: "@unflakable/jest-plugin/dist/runner",
 
+  // Default changed in Jest 29 (see
+  // https://github.com/facebook/jest/blob/94c06ef0aa9b327f3c400610b861e7308b29ee0d/docs/UpgradingToJest29.md).
+  snapshotFormat: {
+    escapeString: true,
+    printBasicPrototype: true,
+  },
+
   testEnvironment: "node",
 
   transform: {