Now that https://bugs.kde.org/show_bug.cgi?id=472219 has been fixed upstream in:
https://sourceware.org/git/?p=valgrind.git;a=commit;h=6ce0979884a8f246c80a098333ceef1a7b7f694d
Add a supression to ignore the bug until we are using a fixed version of Valgrind.
Related to #28072.