Remove Julia nightly for now

I'll add it back in another commit. The tests need more fixes overall.

Author: mkitti

.github/workflows/main.yml

@@ -26,7 +26,6 @@ jobs:
           - '1.6'
           - '1.7'
           - '1.8'
-          - 'nightly'
         exclude:
           - os: ubuntu-latest
             architecture: x86