Relax pip-version constraint in GHA (close #773)

Author: tcompa

.github/workflows/manifest_external_packages.yml

@@ -81,7 +81,7 @@ jobs:
           cache: 'pip'
 
       - name: Update pip
-        run:  python -m pip install pip==24.0
+        run:  python -m pip install --upgrade pip
 
       - name: Install package
         run:  ${{ matrix.cmd_install }}