COMP: Fix "ci" GitHub workflow removing deprecated use of "::set-output"

Fix the following warning:

  The `set-output` command is deprecated and will be disabled soon.
  Please upgrade to using Environment Files.
  For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

.github/actions/slicer-build/entrypoint.sh

@@ -15,4 +15,4 @@ mv ${package_filepath} $GITHUB_WORKSPACE/
 package=$(basename $package_filepath)
 echo "package [${package}]"
 
-echo "::set-output name=package::$package"
+echo "package=$package" >> $GITHUB_OUTPUT