[15.0+] Missing group node inside notebook page nodes

[delvsola]

Some form views examples are missing the <group>...</group> tags inside <notebook><page>...</page></notebook> nodes.

This leads to an improper rendering of the fields inside the view and is misleading for newer developers figuring out form views.

Occurrences of this issue: https://github.com/odoo/documentation/blob/f94085fd8addaad72a2d5d01a1d950dac8e8d59a/content/developer/tutorials/getting_started/07_basicviews.rst?plain=1#L101-L105 https://github.com/odoo/documentation/blob/05637af163b35530daa0dda305f862e84c29519f/content/developer/tutorials/backend.rst?plain=1#L375-L379

[AntoineVDV]

Hi @delvsola, would you mind creating the PR? If needed, you'll find the steps to build the doc locally in the README file ;)