[Backport] Fixed set template syntax in block file

[gelanivishal]

Original Pull Request

#15339

Description

Fixed set template syntax in block file

Fixed Issues (if relevant)

1. Template syntax in block file #15345:Template syntax in block file

Manual testing scenarios

N/A

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• 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)

[sidolov]

Hi @gelanivishal , due to changes in Magento Code Contributions Guide we can't accept such Pull Requests to 2.1 release line. All code cleanup like typos, spelling mistakes, removing unused code, etc should be delivered to 2.3 release line.
Thank you!