update codecov badge

Author: ablaom

README.md

@@ -7,7 +7,7 @@ machine learning or statistics.
 
 [![Lifecycle:Maturing](https://img.shields.io/badge/Lifecycle-Maturing-007EC6)]()
 [![Build Status](https://github.com/JuliaAI/LearnDataFrontEnds.jl/workflows/CI/badge.svg)](https://github.com/JuliaAI/LearnDataFrontEnds.jl/actions)
-[![codecov](https://codecov.io/gh/JuliaAI/LearnDataFrontEnds.jl/graph/badge.svg?token=9IWT9KYINZ)](https://codecov.io/gh/JuliaAI/LearnDataFrontEnds.jl?branch=dev)
+[![codecov](https://codecov.io/gh/JuliaAI/LearnDataFrontEnds.jl/graph/badge.svg?token=tIJyIuCipO)](https://codecov.io/gh/JuliaAI/LearnDataFrontEnds.jl)
 [![Docs](https://img.shields.io/badge/docs-dev-blue.svg)](https://juliaai.github.io/LearnDataFrontEnds.jl/dev/)
 
 A LearnAPI.jl implementation including a data front end from this package gives users the