Update documentation for fail_on_empty_dump

[yamasakih]

What I did

• Update documentation for fail_on_empty_dump (Close to https://github.com/m3dev/gokart/issues/281)

[Hi-king]

@yamasakih Really thanks for fixing the wrong documentation!

LGTM

Anyway, another example to use fail_on_empty_dump in notebook is as follows.

class EmptyTask(gokart.TaskOnKart):
    fail_on_empty_dump: bool = ExplicitBoolParameter(default=True, significant=False) #override TaskOnKart.fail_on_empty_dump
    def run(self):
        df = pd.DataFrame()
        self.dump(df)

gokart.build(EmptyTask())

We can override fail_on_empty_dump on any tasks instead of injecting it from conf

[mski-iksm]

@yamasakih Thank you for fixing the document! LGTM!

[Hi-king]

@yamasakih Thx for your contribution!

[yamasakih]

@Hi-king

Thank you for introducing another way. I thought it was very nice because I thought it was one way to override as you said.

@mski-iksm Thank you for your suggestion!