unify config.h includes

4 jobs for issue/config_h in 50 minutes and 13 seconds (queued for 28 minutes and 3 seconds)
Status Job ID Name Coverage
  Test
passed #20984
dune-2.6

00:23:53

passed #20985
dune-2.7

00:31:37

passed #20986
dune-git

00:34:22

passed #20987
dune-git-full

00:40:58