[CI/CD] Fixes fro the docker images publishing pipeline (#6938)

This PR contains a small number of fixes that have been made to the
release pipeline:
- Fixes docker image publishing for polkadot
- Fixes docker owner in one of the jobs for the polakdot container
- Fixes a description of one of the inputs

.github/scripts/common/lib.sh

@@ -297,7 +297,6 @@ fetch_release_artifacts_from_s3() {
   pwd
   ls -al --color
   popd > /dev/null
-  unset OUTPUT_DIR
 }
 
 # Pass the name of the binary as input, it will

.github/workflows/release-50_publish-docker.yml

@@ -46,7 +46,7 @@ on:
         required: true
 
       stable_tag:
-        description: Tag matching the actual stable release version in the format stableYYMM or stableYYMM-X for patch releases
+        description: Tag matching the actual stable release version in the format polkadpt-stableYYMM(-rcX) or plkadot-stableYYMM-X(-rcX) for patch releases
         required: true
 
 permissions:
@@ -311,9 +311,9 @@ jobs:
           # TODO: The owner should be used below but buildx does not resolve the VARs
           # TODO: It would be good to get rid of this GHA that we don't really need.
           tags: |
-            egorpop/polkadot:${{ steps.fetch-data.outputs.stable }}
-            egorpop/polkadot:latest
-            egorpop/polkadot:${{ needs.fetch-latest-debian-package-version.outputs.polkadot_container_tag }}
+            parity/polkadot:${{ steps.fetch-data.outputs.stable }}
+            parity/polkadot:latest
+            parity/polkadot:${{ needs.fetch-latest-debian-package-version.outputs.polkadot_container_tag }}
           build-args: |
             VCS_REF=${{ github.ref }}
             POLKADOT_VERSION=${{ needs.fetch-latest-debian-package-version.outputs.polkadot_apt_version }}