fix: remove duplicate changelog from release notes

- Remove manual git log changelog from release body
- Rely on generate_release_notes for auto-generated changelog
- Keep custom Docker pull instructions in body
- Avoid duplicate/conflicting changelog content

Author: nanotaboada

.github/workflows/dotnet-cd.yml

@@ -158,10 +158,6 @@ jobs:
             docker pull ghcr.io/${{ env.PACKAGE_NAME }}:latest
             ```
 
-            ## Changes
-
-            ${{ steps.changelog.outputs.changelog }}
-
             ---
 
             📦 **Package:** [ghcr.io/${{ env.PACKAGE_NAME }}](https://github.com/${{ github.repository }}/pkgs/container/dotnet-samples-aspnetcore-webapi)