tests: prevent output in phpunit tests (#1158)

I noticed an accidental `echo` left in a test during a recent review. It's best practice to avoid output during tests. Update PHPUnit config to make CI fail, rather than relying on human code review.

* Modify `ElasticSearchIndexDeleteTest` so it doesn't print output.
* `beStrictAboutOutputDuringTests` marks tests as "risky" if there is output printed.
* `failOnRisky` makes the test suite fail if any tests are marked as "risky".

Bug: T428716

Author: outdooracorn

phpunit.xml

@@ -9,6 +9,8 @@
   xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
   cacheDirectory=".phpunit.cache"
   backupStaticProperties="false"
+  beStrictAboutOutputDuringTests="true"
+  failOnRisky="true"
 >
   <testsuites>
     <testsuite name="Application Test Suite">

tests/Jobs/Integration/ElasticSearchIndexDeleteTest.php

@@ -48,12 +48,11 @@ public function makeRequest($url, $method = 'GET') {
         );
         $response = $curlRequest->execute();
         $err = $curlRequest->error();
-        var_dump($response);
+        $curlRequest->close();
 
         if ($err) {
-            var_dump($err);
+            $this->fail("Request returned an error: {$err}");
         }
-        $curlRequest->close();
 
         return json_decode($response, true);
     }