Don't upload libcudf-example to Anaconda.org (rapidsai#12671)

When initially created, the GitHub Actions scripts that upload conda packages would upload all packages that were built indiscriminately.

As a result, the `libcudf-example` package has been uploading to Anaconda.org. It was not previously uploaded to Anaconda.org prior to migrating to GitHub Actions.

While this isn't a huge deal, I recently added some functionality ([here](rapidsai/shared-workflows#33)) that allows us to specify package names that shouldn't be uploaded to Anaconda.org in our workflows.

This PR adds the `libcudf-example` package to the list of packages that should not be uploaded to Anaconda.org

Authors:
   - AJ Schmidt (https://github.com/ajschmidt8)

Approvers:
   - Ray Douglass (https://github.com/raydouglass)

.github/workflows/build.yaml

@@ -52,6 +52,7 @@ jobs:
       branch: ${{ inputs.branch }}
       date: ${{ inputs.date }}
       sha: ${{ inputs.sha }}
+      skip_upload_pkgs: libcudf-example
   wheel-build-cudf:
     secrets: inherit
     uses: rapidsai/shared-action-workflows/.github/workflows/wheels-manylinux-build.yml@cuda-118