fix(docs, processing_time_checker): add the default fields so that the documentation build will not fail

[Owen-Liuyuxuan]

Description

https://autowarefoundation.github.io/autoware.universe/main/system/autoware_processing_time_checker/

Add the default fields for processing_time_topic_name_list so that the documentation build will not fail.

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Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.