Remove obviated build workflow step for removing Linux channel file

In addition to the builds, when a nightly or production release is published, a "channel update info file" is also
uploaded to Amazon S3 by the "Arduino IDE" GitHub Actions workflow. The IDE checks the channel file on the server to get
information about available updates.

Previously the Linux production release builds were being remade manually due to the ones produced by GitHub Actions not
being compatible with older distro versions due to a dynamically linked dependency. For this reason, a step was
temporarily added to the workflow to cause it to not upload the Linux channel file in order to avoid Linux users from
receiving an update offer before the limited compatibility automated build had been replaced with the manually produced
build.

The automated build system has been adjusted to produce Linux builds with the intended range of compatibility, but the
step that deleted the channel file was not removed at that time. The obviated step is hereby removed in order to allow
complete releases to be published by the workflow.

Author: per1234

Diff for: .github/workflows/build.yml

@@ -595,13 +595,6 @@ jobs:
           file_glob: true
           body: ${{ needs.changelog.outputs.BODY }}
 
-      # Temporary measure to prevent release update offers before the manually produced builds are uploaded.
-      # The step must be removed once fully automated builds are regained.
-      - name: Remove "channel update info files" related to manual builds
-        run: |
-          # See: https://github.com/arduino/arduino-ide/issues/2018
-          rm "${{ env.JOB_TRANSFER_ARTIFACT }}/stable-linux.yml"
-
       - name: Publish Release [S3]
         if: needs.build-type-determination.outputs.publish-to-s3 == 'true'
         uses: docker://plugins/s3