Update test matrix to allow support for AMP

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
       max-parallel: 2
       matrix:
         python-version: [3.6, 3.7, 3.8]
-        torch-version: [1.4.0, 1.5.0]
+        torch-version: [1.6.0, 1.7.0]
 
     steps:
       - uses: actions/checkout@v1