Replace deprecated usage of db_transaction

Alexey, thanks for looking at this!!!

1. +++ b/lingotek.services.yml
   @@ -43,7 +43,7 @@ services:
   -    arguments: ['@lingotek', '@lingotek.language_locale_mapper', '@lingotek.configuration', '@lingotek.config_translation', '@entity_type.manager', '@language_manager', '@entity_field.manager']
   +    arguments: ['@lingotek', '@lingotek.language_locale_mapper', '@lingotek.configuration', '@lingotek.config_translation', '@entity_type.manager', '@language_manager', '@database', '@entity_field.manager']
   
   +++ b/src/LingotekContentTranslationService.php
   @@ -91,10 +99,12 @@ class LingotekContentTranslationService implements LingotekContentTranslationSer
   -  public function __construct(LingotekInterface $lingotek, LanguageLocaleMapperInterface $language_locale_mapper, LingotekConfigurationServiceInterface $lingotek_configuration, LingotekConfigTranslationServiceInterface $lingotek_config_translation, EntityTypeManagerInterface $entity_type_manager, LanguageManagerInterface $language_manager, EntityFieldManagerInterface $entity_field_manager = NULL) {
   +  public function __construct(LingotekInterface $lingotek, LanguageLocaleMapperInterface $language_locale_mapper, LingotekConfigurationServiceInterface $lingotek_configuration, LingotekConfigTranslationServiceInterface $lingotek_config_translation, EntityTypeManagerInterface $entity_type_manager, LanguageManagerInterface $language_manager, Connection $connection, EntityFieldManagerInterface $entity_field_manager = NULL) {
   

   Let's put @database as the last argument per backwards compatibility, and default to NULL.

2. +++ b/src/LingotekContentTranslationService.php
   @@ -105,6 +115,7 @@ class LingotekContentTranslationService implements LingotekContentTranslationSer
          @trigger_error('The entity_field.manager service must be passed to LingotekContentTranslationService::__construct, it is required before Lingotek 9.x-1.0. See https://www.drupal.org/node/2549139.', E_USER_DEPRECATED);
          $entity_field_manager = \Drupal::service('entity_field.manager');
        }
   +    $this->connection = $connection;
        $this->entityFieldManager = $entity_field_manager;
   

   If $connection is null, trigger an error and assign it from the container as we do with $entity_field_manager.

Great!

+++ b/src/LingotekContentTranslationService.php
@@ -105,7 +115,12 @@ class LingotekContentTranslationService implements LingotekContentTranslationSer
+      @trigger_error('The database service must be passed to LingotekContentTranslationService::__construct, it is required before Lingotek 9.x-1.0. See https://www.drupal.org/node/2549139.', E_USER_DEPRECATED);

That's referencing a wrong change record (applies for entity_manager, not for this deprecation).
Please link to https://www.drupal.org/node/2993033

You did!! Thanks a lot :-)

Committed 73177fe and pushed to 8.x-2.x. Thanks, Alexey!