ci: drop --pre-release rc from publish workflow

The publish workflow hardcoded --pre-release rc, so ShipIt kept cutting
5.0.0-rc.N release PRs (e.g. #261) even after the justfile recipe was
updated. Remove the flag so ShipIt produces stable releases.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dbrattli

.github/workflows/publish.yml

@@ -32,7 +32,7 @@ jobs:
         run: dotnet tool restore
 
       - name: ShipIt (Pull Request)
-        run: dotnet shipit --pre-release rc
+        run: dotnet shipit
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}