Remove references to cirrus, mostly in doc comments. (#161529)

Towards https://github.com/flutter/flutter/issues/161387.

dev/customer_testing/ci.sh

@@ -5,7 +5,7 @@
 
 # This should match the ci.bat file in this directory.
 
-# This is called from .cirrus.yml and the LUCI recipes:
+# This is called from the LUCI recipes:
 # https://github.com/flutter/flutter/blob/main/dev/bots/suite_runners/run_customer_testing_tests.dart
 
 set -ex

dev/devicelab/lib/framework/browser.dart

@@ -45,7 +45,7 @@ class ChromeOptions {
   final int windowHeight;
 
   /// Launches code in "headless" mode, which allows running Chrome in
-  /// environments without a display, such as LUCI and Cirrus.
+  /// environments without a display, such as LUCI.
   final bool? headless;
 
   /// The port Chrome will use for its debugging protocol.

docs/platforms/android/New-Android-version.md

@@ -63,12 +63,8 @@ In the framework, update the following `.ci.yaml` entry:
 
 In the engine, you may follow [Upgrading Engine's Android API version](https://github.com/flutter/flutter/blob/main/docs/platforms/android/Upgrading-Engine's-Android-API-version.md) to update the AVD dependency.
 
-Example Framework PR: https://github.com/flutter/flutter/pull/152498, Example Engine PR: https://github.com/flutter/engine/pull/54186
-
-In flutter/packages, modify https://github.com/flutter/packages/blob/main/.cirrus.yml “firebase_test_lab_script”
-Specifically the value for “--device” `./script/tool_runner.sh firebase-test-lab --device model=redfin,version=30 --exclude=script/configs/exclude_integration_Android.yaml`.
-
-Example PR: https://github.com/flutter/packages/pull/4430
+- Example Framework PR: <https://github.com/flutter/flutter/pull/152498>.
+- Example Engine PR: <https://github.com/flutter/engine/pull/54186>.
 
 #### Update documentation
 

engine/src/flutter/lib/web_ui/dev/firefox_installer.dart

@@ -29,8 +29,6 @@ Future<BrowserInstallation> getOrInstallFirefox(
   String requestedVersion, {
   StringSink? infoLog,
 }) async {
-  // These tests are aimed to run only on the Linux containers in Cirrus.
-  // Therefore Firefox installation is implemented only for Linux now.
   if (!io.Platform.isLinux && !io.Platform.isMacOS) {
     throw UnimplementedError(
       'Firefox Installer is only supported on Linux '

engine/src/flutter/testing/benchmark/bin/parse_and_send.dart

@@ -92,9 +92,7 @@ Future<void> main(List<String> args) async {
 
   // The data will be sent to the Datastore of the GCP project specified through
   // environment variable BENCHMARK_GCP_CREDENTIALS, or TOKEN_PATH/GCP_PROJECT.
-  // The engine Cirrus job has currently configured the GCP project to
-  // flutter-cirrus for test. We'll eventually migrate to flutter-infra project
-  // once the test is done.
+  // The engine LUCI job writes it to the `flutter-infra` project.
   final FlutterDestination destination = await connectFlutterDestination();
   await destination.update(
     pointsAndDate.points,

packages/flutter_goldens/test/comparator_selection_test.dart

@@ -168,7 +168,7 @@ void main() {
       _Comparator.skip,
     );
 
-    // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect.
+    // On Luci, with Gold, post-submit. Flutter root has no effect.
     expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true), _Comparator.post);
     expect(
       _testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasFlutterRoot: true),