ENH: to_graphics now has `no_shadow` option.

Summary

Just a small new option for plantuml generation

Focus

• Does this option do what it should?
• Are there any negative side-effects?

Test Environment

import caosdb as db; from caosdb.utils import plantuml
cont = db.Container().append(db.RecordType(name="test"))
plantuml.to_graphics(cont, "test_with")
plantuml.to_graphics(cont, "test_without", no_shadow=True)

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