add the 8-gpu test badge and use correct links for the integration test badges

ghstack-source-id: f198ee4
Pull Request resolved: #390

Author: tianyu-l

README.md

@@ -1,4 +1,5 @@
-[![4 GPU Integration Test](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_4gpu.yaml/badge.svg?branch=main)](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_4gpu.yaml)
+[![4 GPU Integration Test](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_4gpu.yaml/badge.svg?branch=main)](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_4gpu.yaml?query=branch%3Amain)
+[![8 GPU Integration Test](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_8gpu.yaml/badge.svg?branch=main)](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_8gpu.yaml?query=branch%3Amain)
 
 # torchtitan