$context removed from hook_entity_view_mode_alter()

Before, the implementations of hook_entity_view_mode_alter() hook received $context array as 3rd argument, that was supposed to provide some additional context information. In practice, the $context was always empty since #2073217: Remove the $langcode parameter from the entity view/render system was committed.
It was decided to remove it as it's not necessary.

Before:

function hook_entity_view_mode_alter(&$view_mode, Drupal\Core\Entity\EntityInterface $entity, $context) {
  if ($entity->getEntityTypeId() == 'node' && $view_mode == 'teaser') {
    $view_mode = 'my_custom_view_mode';
  }
}

After:

function hook_entity_view_mode_alter(&$view_mode, Drupal\Core\Entity\EntityInterface $entity) {
  if ($entity->getEntityTypeId() == 'node' && $view_mode == 'teaser') {
    $view_mode = 'my_custom_view_mode';
  }
}