Update README.md

Fix badge in README

Author: kojix2

README.md

@@ -1,6 +1,6 @@
 # ruby-hdf5
 
-[![test](https://github.com/kojix2/c2ffi4rb/actions/workflows/ci.yml/badge.svg)](https://github.com/kojix2/c2ffi4rb/actions/workflows/ci.yml)
+[![test](https://github.com/red-data-tools/ruby-hdf5/actions/workflows/test.yml/badge.svg)](https://github.com/red-data-tools/ruby-hdf5/actions/workflows/test.yml)
 
 experimental Ruby bindings for the HDF5 library