Relative links in README.md assume existance of "master" branch

I've a project with no "master" branch and the default branch is correctly set to "svn-trunk". The relative links in the README.md file shown in the project main page bogusly points to the unexistent "master" branch, which is then a 404.

See https://gitlab.com/postgis/postgis

The README.md from the "files" section correctly stays in its branch.

Added markdown label

Status changed to closed

Closing in favor of #2707 (closed)

mentioned in issue #2707 (closed)

Submitted a fix in MR 1801

mentioned in commit 3777b233

mentioned in merge request !14785