Enable publishes to nightly anaconda on pushes to main (#55)

The workflow setup currently does not publish to
https://anaconda.org/rapidsai-nightly and only publishes to
https://anaconda.org/rapidsai (via tags); this introduces an issue where
conda solves which use the `rapisai-nightly` channel fails.

So this PR updates the setup to publish to `rapidsai-nightly` on pushes
to main.

Author: AyodeAwe

.github/workflows/build-main.yaml

@@ -14,5 +14,5 @@ jobs:
     uses: ./.github/workflows/checks-and-builds.yaml
     with:
       build_type: branch
-      publish: false
+      publish: true
     secrets: inherit