chore(deps): update app engine samples to PHP 8.4 (#2139)

Author: Hemant28codes

appengine/flexible/helloworld/app.yaml

@@ -4,7 +4,7 @@ env: flex
 runtime_config:
   document_root: web
   operating_system: ubuntu22
-  runtime_version: 8.3
+  runtime_version: 8.4
 
 # This sample incurs costs to run on the App Engine flexible environment.
 # The settings below are to reduce costs during testing and are not appropriate

appengine/standard/getting-started/README.md

@@ -1,7 +1,7 @@
-# Getting Started on App Engine for PHP 8.1
+# Getting Started on App Engine for PHP 8.4
 
 This sample demonstrates how to deploy a PHP application which integrates with
-Cloud SQL and Cloud Storage on App Engine Standard for PHP 8.1. The tutorial
+Cloud SQL and Cloud Storage on App Engine Standard for PHP 8.4. The tutorial
 uses the Slim framework.
 
 ## View the [full tutorial](https://cloud.google.com/appengine/docs/standard/php-gen2/building-app)

appengine/standard/getting-started/app.yaml

@@ -1,7 +1,7 @@
 # See https://cloud.google.com/appengine/docs/standard/php/config/appref for a
 # complete list of `app.yaml` directives.
 
-runtime: php81
+runtime: php84
 
 env_variables:
     GOOGLE_STORAGE_BUCKET: ""