fbeta_score does not accept beta=0

[wdevazelhes]

fbeta_score does not accept beta=0. In this case I agree that we could use precision_score which is the same, but is there a reason why this fbeta_score(... beta=0) would be forbidden ? If not I'd be happy to provide a PR. These are the lines that I would delete (plus I would provide a test):

scikit-learn/sklearn/metrics/classification.py

Lines 1028 to 1029 in 7389dba

	if beta <= 0:
	raise ValueError("beta should be >0 in the F-beta score")

What is more, this case is even mentioned in the documentation ("beta -> 0 considers only precision, beta -> inf only recall)"), so we would reasonably expect it to work ? https://scikit-learn.org/stable/modules/generated/sklearn.metrics.fbeta_score.html

[qinhanmin2014]

Seems reasonable from my side.

[corona10]

@qinhanmin2014 Can I take a look at this issue?

[qinhanmin2014]

@qinhanmin2014 Can I take a look at this issue?

Welcome to contribute.