Replace deprecated EntityManagerInterface uses

I tested the patch and it worked for me.

cit008490cpsubuntu:taxonomy_menu progestag* 8.x-3.x$ find .  -type f \( -name '*.php' -or -name '*.module' -or -name '*.yml' \) -exec grep -i --color=auto entitymanager {} \+
./src/TaxonomyMenuHelper.php:use Drupal\Core\Entity\EntityManagerInterface;
./src/TaxonomyMenuHelper.php:  public function __construct(EntityManagerInterface $entity_manager, MenuLinkManagerInterface $manager) {
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:use Drupal\Core\Entity\EntityManagerInterface;
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:   * @var \Drupal\Core\Entity\EntityManager
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:  protected $entityManager;
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:    EntityManagerInterface $entity_manager,
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:    $this->entityManager = $entity_manager;
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:    $link = $this->entityManager->getStorage('taxonomy_term')
./src/Plugin/Menu/TaxonomyMenuMenuLink.php:    $link = $this->entityManager->getStorage('taxonomy_term')

cit008490cpsubuntu:taxonomy_menu progestag* 8.x-3.x$ patch -p1 < ~/drupal/Patches/taxonomy_menu-replace_deprecated_entity_manager_interface_uses-2857550-2.patch
patching file src/Plugin/Menu/TaxonomyMenuMenuLink.php
patching file src/TaxonomyMenuHelper.php

cit008490cpsubuntu:taxonomy_menu progestag* 8.x-3.x$ find .  -type f \( -name '*.php' -or -name '*.module' -or -name '*.yml' \) -exec grep -i --color=auto entitymanager {} \+ | wc -l
0

Reviewed the patch #2 and verified that EntityManager is replaced by EntityTypeManager.
+1 to RTBC

Thanks for the contribution!