Update release.yml

Author: tschaume

.github/workflows/release.yml

@@ -32,6 +32,7 @@ jobs:
           python${{ matrix.python-version }} -m pip install --upgrade pip packaging wheel build
           python${{ matrix.python-version }} -m pip install `grep numpy== requirements/ubuntu-latest_py${{ matrix.python-version }}_extras.txt`
           python${{ matrix.python-version }} -m pip install -r requirements/ubuntu-latest_py${{ matrix.python-version }}_extras.txt
+          python${{ matrix.python-version }} -m pip install --upgrade pip
           python${{ matrix.python-version }} -m pip install --no-deps .[server]
           
       - name: Build package