Revert "CI: work around Gitlab Cobertura parsing quirk"

This reverts commit f6ff85b1.

This hack should not be needed anymore for Gitlab at freedesktop.org.

Mainly I worry that it might throw pycobertura off track in a
future patch.

See also: !1027



Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>