ci: pipeline_message: ignore error_type errors

Currently marge only ignores `error_type` when the type is None.
But other error_types are equally uninteresting e.g. `error_type: Jobs`.

Example:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32677#note_2711470
https://gitlab.freedesktop.org/mesa/mesa/-/pipelines/1333563

Ignore the phrase `error_type` so marge will provide more useful comments.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32773>

.marge/hooks/pipeline_message.py

@@ -219,7 +219,7 @@ async def search_job_log_for_errors(session, project_id, job):
     ignore_list = [
         "aborting",
         "error_msg      : None",
-        "error_type     : None",
+        "error_type",
         "exit code",
         "exit status",
         "exiting now",

bin/ci/test/test_pipeline_message.py

@@ -174,7 +174,7 @@ async def test_search_job_log_for_errors(mock_get_job_log):
 error_msg: something useful
 error aborting
 error_msg      : None
-error_type     : None
+error_type     : Job
 [0Ksection_end:1734694783:job_data
 [0K
 [0m11:39:43.438: [1mFinished executing LAVA job in the attempt #3 [0m