Remove explicit CI tests on v1.8 (#798)

Now that `v1` points to `v1.8`

Author: jishnub

.github/workflows/ci.yml

@@ -17,7 +17,6 @@ jobs:
         version:
           - '1.6'
           - '1'
-          - '^1.8.0-0'
         os:
           - ubuntu-latest
           - macOS-latest