fix(ci): remove duplicate "What's Changed" heading in release draft

The release workflow set a hardcoded body of '## What's Changed' and
also enabled generate_release_notes (which emits its own '## What's
Changed' section), then stacked them via append_body, producing two
identical headings in every draft.

Drop the hardcoded body and append_body; generate_release_notes already
produces a complete 'What's Changed' section plus the Full Changelog link.

Author: mrrobot47

.github/workflows/release.yaml

@@ -19,10 +19,6 @@ jobs:
     - name: Publish a Draft Release
       uses: softprops/action-gh-release@a06a81a03ee405af7f2048a818ed3f03bbf83c7b # v2.5.0
       with:
-        body: |
-          ## What's Changed
-
         draft: true  # Creates a Draft Release
         name: ${{ env.release_name }}
         generate_release_notes: true
-        append_body: true