"Create Merge Request" from issue always appends notation to close original issue

Summary

Every merge request is closing issue by default even if there is a defined merge request default template.

Steps to reproduce

• Define default description template for merge requests for the project (you can do this in "Merge request settings"). For example template "My template here"
• Open an issue
• Click "Create merge request" button

Expected results: Merge request with description "My template here" is created.

Results: Merge request with description "My template here \n Closes #issue_number" is created.

Example Project

https://gitlab.com/jeremeeva/merge-request-bug-project

What is the current bug behavior?

Merge request with description with last line "Closes #issue_number" is created.

What is the expected correct behavior?

Merge request is be created only with usage of default description template for merge requests.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Possible fixes

Do not add "Closes #issue_number" line to merge request description if there is default merge request template is defined.