feat: update apikey sample for client option support

Author: bshaffer

auth/src/auth_cloud_apikey.php

@@ -44,8 +44,7 @@ function auth_cloud_apikey(string $projectId, string $location, string $apiKey):
 
     // Create a client.
     $productSearchClient = new ProductSearchClient([
-        // STEP 1: Use an insecure credentials wrapper to bypass the application default credentials.
-        'credentials' => new InsecureCredentialsWrapper(),
+        'apiKey' => $apiKey,
     ]);
 
     // Prepare the request message.
@@ -55,10 +54,7 @@ function auth_cloud_apikey(string $projectId, string $location, string $apiKey):
     // Call the API and handle any network failures.
     try {
         /** @var PagedListResponse $response */
-        $response = $productSearchClient->listProducts($request, [
-            // STEP 2: Pass in the API key with each RPC call as a "Call Option"
-            'headers' => ['x-goog-api-key' => [$apiKey]],
-        ]);
+        $response = $productSearchClient->listProducts($request);
 
         /** @var Product $element */
         foreach ($response as $element) {