Cannot serialize watcher trigger when kwargs have datetime

[dstandish]

Body

See test test_add_asset_trigger_references, which i will be marking xfail in my pr to enable serdags for all dagmaker usage.

Committer

• I acknowledge that I am a maintainer/committer of the Apache Airflow project.

[uranusjr]

I pushed a commit 7581992 to #50359 to resolve this.

[vatsrahul1001]

This is done