Fix the typo of attribute name decision_score_

[OldPanda]

The argument should be decision_score_ other than decision_scores_ in a model object according to the definition of class Detector

[coveralls]

Pull Request Test Coverage Report for Build 5652650448

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.562%

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Totals
Change from base Build 5595818306:	0.0%
Covered Lines:	2503
Relevant Lines:	2514

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💛 - Coveralls