Unused local variables from LocalTaskManagerTest file

Problem/Motivation

In core/tests/Drupal/Tests/Core/Menu/LocalTaskManagerTest.php file in function testGetTasksBuildWithCacheabilityMetadata() $local_tasks is initialized but never used.

Proposed resolution

Remove unused $local_tasks variable.

public function testGetTasksBuildWithCacheabilityMetadata() {
...... 

       ->willReturn(new ParameterBag());
 
     $cacheability = new CacheableMetadata();
-    $local_tasks = $this->manager->getTasksBuild('menu_local_task_test_tasks_view', $cacheability);
-
     // Ensure that all cacheability metadata is merged together.
     $this->assertEquals(['tag.example1', 'tag.example2'], $cacheability->getCacheTags());
     $this->assertEquals(['context.example1', 'context.example2', 'route', 'user.permissions'], $cacheability->getCacheContexts());