fix: disable automatic releases to test.pypi.org

[test.]pypi.org reject uploads of distributions with an already
  existing version number.

Publishing to testpypi on every commit therefore does not work
  in the current versioning setup since it leads to
  duplicate release versions.

.github/workflows/publish-to-pypi.yml

@@ -1,5 +1,5 @@
 # derived from https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/#the-whole-ci-cd-workflow
-name: Publish Python 🐍 distribution 📦 to PyPI and TestPyPI
+name: Publish Python 🐍 distribution 📦 to PyPI
 
 on: push
 
@@ -115,28 +115,4 @@ jobs:
       run: >-
         gh release upload
         "$GITHUB_REF_NAME" dist/**
-        --repo "$GITHUB_REPOSITORY"
-
-  publish-to-testpypi:
-    name: Publish Python 🐍 distribution 📦 to TestPyPI
-    needs:
-    - build
-    runs-on: ubuntu-latest
-
-    environment:
-      name: testpypi
-      url: https://test.pypi.org/p/d3lta  # pypi is case insensitive so d3lta == D3lta
-
-    permissions:
-      id-token: write  # IMPORTANT: mandatory for trusted publishing
-
-    steps:
-    - name: Download all the dists
-      uses: actions/download-artifact@v4
-      with:
-        name: python-package-distributions
-        path: dist/
-    - name: Publish distribution 📦 to TestPyPI
-      uses: pypa/gh-action-pypi-publish@release/v1
-      with:
-        repository-url: https://test.pypi.org/legacy/
+        --repo "$GITHUB_REPOSITORY"