Update filter CLI option docs (v29.1). Related to issue #13222

Author: brunocabral88

website/versioned_docs/version-29.1/CLI.md

@@ -202,11 +202,13 @@ Alias: `-e`. Use this flag to show full diffs and errors instead of a patch.
 
 ### `--filter=<file>`
 
-Path to a module exporting a filtering function. This asynchronous function receives a list of test paths which can be manipulated to exclude tests from running by returning an object with the "filtered" property. Especially useful when used in conjunction with a testing infrastructure to filter known broken, e.g.
+Path to a module exporting a filtering function. This asynchronous function receives a list of test paths which can be manipulated to exclude tests from running by returning an object with shape `{ filtered: Array<{ test: string }> }`. Especially useful when used in conjunction with a testing infrastructure to filter known broken tests, e.g.
 
 ```js title="my-filter.js"
 module.exports = testPaths => {
-  const allowedPaths = testPaths.filter(filteringFunction); // ["path1.spec.js", "path2.spec.js", etc]
+  const allowedPaths = testPaths.filter(filteringFunction)
+    .map(test => ({ test })); // [{ test: "path1.spec.js" }, { test: "path2.spec.js" }, etc]
+
   return {
     filtered: allowedPaths,
   };