Documentation deploy

[dario-coscia]

Describe the bug The documentation workflow fails to deploy. This is mainly due to the sphinx dependencies in EXTRA in setup.py

EXTRAS = {
    'docs': [
        'sphinx',
        'sphinx_rtd_theme',
        'sphinx_copybutton',
        'sphinx_design',
        'pydata_sphinx_theme'
        ],
    'test': ['pytest', 'pytest-cov'],
}

To Reproduce See https://github.com/mathLab/PINA/actions/runs/10687371959