Use sum() directly over boolean values in logging statements

[suhaibmujahid]

An example of not using the boolean values directly:

bugbug/bugbug/models/annotate_ignore.py

Lines 118 to 121 in d454491

	logger.info(
	"%d commits that cannot be ignored",
	sum(1 for label in classes.values() if label == 0),
	)

Preferred approach:

 logger.info( 
     "%d commits that cannot be ignored", 
     sum(label == 0 for label in classes.values()), 
 )