Revert ".gitlab-ci.yml: Use fedora-30 instead debian 9 for overnigth tests"

This reverts commit 08ead05bbe24a6de94e26b1121e5aa8dd341f691.

This commit was introduced to fix #1097, however it appears to not
be needed anymore after e48a03b2b226f1748edf5c2d5e28093da7ca6a1a which
uses a newer version of bst-external.

However, moving to fedora-30 runtime DID introduce a regression with
the ostree plugin, causing out-of-sync error messages to consistently
occur whenever fetching an ostree source.

Reverting to the old debian 9 docker image appears to fix the
ostree installation to work, fixing the afore mentioned regression
outlined in issue #1098.

This fixes #1098.
1 file changed