Onboarding wizard regressions

Several issues here:

• scroll view does not stop at bounds
• the default view is too tall (the first window the user sees (at default size) has hidden options for no good reason)
• the onboarding window is resizable (now it differs only in size from the main window)

added BacklogMedium UI/UX labels

added good-first-issue label

assigned to @agsantos

added SprintIn progress label

https://review.jami.net/c/jami-client-qt/+/25164

i would keep the size of default view for now

added SprintTo review label and removed SprintIn progress label

mentioned in commit 8fd7c70d

done?

added SprintDone label and removed SprintTo review label

closed

removed SprintDone label