Otherwise unittest thinks the function is a test itself and runs it
accordingly, and then raises a deprecation warning because
return values are not permitted from test functions
when a script calls Processing.initialize() if they are not
already loaded
This means the following ugly code can be avoided:
Processing.initialize()
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms(QgsApplication.processingRegistry()))
QgsApplication.processingRegistry().addProvider(Qgs3DAlgorithms(QgsApplication.processingRegistry()))
and instead the call to Processing.initialize() is sufficient to load
ALL providers
Fixes#41310
