Fix phpstan errors

Author: norkunas

src/Endpoints/Indexes.php

@@ -145,7 +145,7 @@ public function update(array $body): Task
     public function delete(): Task
     {
         $response = $this->http->delete(self::PATH.'/'.$this->uid);
-        assert($response !== null);
+        \assert(null !== $response);
 
         return Task::fromArray($response);
     }

tests/Endpoints/DocumentsTest.php

@@ -840,8 +840,8 @@ public function testUpdateDocumentsCsvInBatches(): void
 
         $tasks = $index->updateDocumentsCsvInBatches($replacement, 1);
         self::assertCount(2, $tasks);
-        foreach ($tasks as $task) {
-            $index->waitForTask($task->getTaskUid());
+        foreach ($tasks as $enqueuedTask) {
+            $index->waitForTask($enqueuedTask->getTaskUid());
         }
 
         $response = $index->getDocument(888221515);
@@ -903,8 +903,8 @@ public function testUpdateDocumentsNdjsonInBatches(): void
 
         $tasks = $index->updateDocumentsNdjsonInBatches($replacement, 1);
         self::assertCount(2, $tasks);
-        foreach ($tasks as $task) {
-            $index->waitForTask($task->getTaskUid());
+        foreach ($tasks as $enqueuedTask) {
+            $index->waitForTask($enqueuedTask->getTaskUid());
         }
 
         $response = $index->getDocument(412559401);