Remove nightly because it's scary

Author: Will Kimmerer

.github/workflows/ci.yml

@@ -19,7 +19,6 @@ jobs:
         version:
           - '1.6' # Replace this with the minimum Julia version that your package supports. E.g. if your package requires Julia 1.5 or higher, change this to '1.5'.
           - '1' # Leave this line unchanged. '1' will automatically expand to the latest stable 1.x release of Julia.
-          - 'nightly'
         os:
           - ubuntu-latest
         arch: