Update zend-soap #37

[cieslix]

Description

Update zend-soap to the version that supports PHP 7.2 - ver. 2.7.0 composer.lock already has zend-soap in version 2.7.0, this information was missing in composer.json.

Fixed Issues (if relevant)

Update zend-soap https://github.com/magento-engcom/php-7.2-support/issues/37

Contribution checklist

• [x] Pull request has a meaningful description of its purpose
• [x] All commits are accompanied by meaningful commit messages
• [x] All new or changed code is covered with unit/integration tests (if applicable)
• [ ] All automated tests passed successfully (all builds on Travis CI are green)