config/pipeline.yaml: Disable KUnit tests on chromiumos tree

KUnit tests are enabled by default on all trees. Since a different set
of initial tests will be enabled on the chromiumos tree, disable KUnit
tests for now.

Signed-off-by: Laura Nao <laura.nao@collabora.com>

Author: laura-nao

config/pipeline.yaml

@@ -1854,6 +1854,9 @@ jobs:
     kind: job
     image: ghcr.io/kernelci/{image_prefix}gcc-12:x86-kunit-kernelci
     kcidb_test_suite: kunit
+    rules:
+      tree:
+      - '!chromiumos'
 
   kunit-x86_64:
     <<: *kunit-job