CI: Use scientific-python/upload-nightly-action

* Use the scientific-python/upload-nightly-action GitHub Action to
  upload the nightly wheels to the scientific-python-nightly-wheels
  Anaconda Cloud package index
  (https://anaconda.org/scientific-python-nightly-wheels).
  For security best practices pin at the commit sha corresponding to the
  last stable release and let Dependabot update the commit sha and
  comment as new releases come out.
   - c.f. https://github.com/scientific-python/upload-nightly-action

Author: matthewfeickert

.github/workflows/nightlies.yml

@@ -58,22 +58,11 @@ jobs:
           mv *.whl dist/
           ls -l dist/
 
-        # N.B. anaconda-client is only maintained on the main channel
-      - name: Install anaconda-client
-        uses: mamba-org/setup-micromamba@v1
-        with:
-          environment-name: nightlies
-          create-args: anaconda-client=1.10.0
-          condarc: |
-            channels:
-              - main
-
       - name: Upload wheels to Anaconda Cloud as nightlies
-        run: |
-          anaconda --token ${{ secrets.ANACONDA_ORG_UPLOAD_TOKEN }} upload \
-            --user scientific-python-nightly-wheels \
-            --skip-existing \
-            dist/matplotlib-*.whl
+        uses: scientific-python/upload-nightly-action@8f0394fd2aa0c85d7364a9958652e8994e06b23c # 0.1.0
+        with:
+          artifacts_path: dist
+          anaconda_nightly_upload_token: ${{ secrets.ANACONDA_ORG_UPLOAD_TOKEN }}
 
       - name: Remove old uploads to save space
         run: |