fix codecov badge

Author: maltezfaria

README.md

@@ -4,7 +4,7 @@
 [![Dev](https://img.shields.io/badge/docs-dev-blue.svg)](https://WaveProp.github.io/WavePropBase.jl/dev)
 [![Build
 Status](https://github.com/WaveProp/WavePropBase/workflows/CI/badge.svg)](https://github.com/WaveProp/WavePropBase.jl/actions)
-[![codecov](https://codecov.io/gh/WaveProp/WavePropBase/branch/main/graph/badge.svg?token=codJo03vp6)](https://codecov.io/gh/WaveProp/WavePropBase.jl)
+[![codecov](https://codecov.io/gh/WaveProp/WavePropBase.jl/branch/main/graph/badge.svg?token=codJo03vp6)](https://codecov.io/gh/WaveProp/WavePropBase.jl)
 
 This package implements the interface used throughout the
 [*WaveProp*](https://github.com/WaveProp) organization, as well as some basic