Remove expilcit test on v1.8 (#22)

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

Author: jishnub

.github/workflows/ci.yml

@@ -12,7 +12,6 @@ jobs:
         version:
           - '1.5'
           - '1'
-          - '^1.8.0-0'
         os:
           - ubuntu-latest
           - macOS-latest