Closes text is duplicated when opening an MR from source branch that starts with issue number

Summary

The text Closes #1234 is duplicated when opening an MR from a source branch that starts with the issue number.

Steps to reproduce

1. Create a branch that starts with an issue number such as <>
2. Open an MR
3. Observe the Closes #1234 text duplicated in the MR description

Example Project

I encountered this with https://gitlab.com/gitlab-org/gitlab and https://gitlab.com/gitlab-org/quality/triage-ops/ and asked on Slack here: https://gitlab.slack.com/archives/CETG54GQ0/p1599142165284400

What is the current bug behavior?

Closes #1234 is duplicated in the MR description

What is the expected correct behavior?

Closes #1234 is not duplicated in the MR description

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Possible fixes

This text can be manually removed so it's not a high severity issue but annoying.