doc: remove experimental abortcontroller flag

doc/api/cli.md

@@ -253,21 +253,6 @@ effort to report stack traces relative to the original source file.
 Overriding `Error.prepareStackTrace` prevents `--enable-source-maps` from
 modifying the stack trace.
 
-### `--experimental-abortcontroller`
-
-<!-- YAML
-added:
-  - v15.0.0
-  - v14.17.0
-changes:
-  - version: v15.0.0
-    pr-url: https://github.com/nodejs/node/pull/33527
-    description: --experimental-abortcontroller is no longer required.
--->
-
-`AbortController` and `AbortSignal` support is enabled by default.
-Use of this command-line flag is no longer required.
-
 ### `--experimental-import-meta-resolve`
 
 <!-- YAML
@@ -1559,7 +1544,6 @@ Node.js options that are allowed are:
 * `--dns-result-order`
 * `--enable-fips`
 * `--enable-source-maps`
-* `--experimental-abortcontroller`
 * `--experimental-import-meta-resolve`
 * `--experimental-json-modules`
 * `--experimental-loader`

test/parallel/test-process-env-allowed-flags-are-documented.js

@@ -104,6 +104,7 @@ assert(undocumented.delete('--no-node-snapshot'));
 assert(undocumented.delete('--loader'));
 assert(undocumented.delete('--verify-base-objects'));
 assert(undocumented.delete('--no-verify-base-objects'));
+assert(undocumented.delete('--experimental-abortcontroller'));
 
 // Remove negated versions of the flags.
 for (const flag of undocumented) {