Revert "include postgres image in kotsadm airgap bundle (#1686)"

This reverts commit ad74b82.

.github/workflows/kotsadm.yaml

@@ -768,7 +768,7 @@ jobs:
 
   build_airgap:
     runs-on: ubuntu-18.04
-    needs: [release_go_api_tagged, release_operator_tagged, build_minio_tagged, build_postgres_tagged]
+    needs: [release_go_api_tagged, release_operator_tagged, build_minio_tagged]
     steps:
     - name: Get the version
       if: startsWith(github.ref, 'refs/tags/')
@@ -804,13 +804,6 @@ jobs:
         name: kotsadm-minio-image
         path: ./docker-archive
 
-    - name: Download kotsadm-postgres image
-      if: ${{ steps.get_tag.outputs.GIT_TAG != '' }}
-      uses: actions/download-artifact@v2.0.8
-      with:
-        name: kotsadm-postgres-image
-        path: ./docker-archive
-
     - name: Get Release
       if: ${{ steps.get_tag.outputs.GIT_TAG != '' }}
       id: get_release