IBX-3723: Upgrading DXP flavour

[adriendupuis]

Question	Answer
JIRA Ticket	IBX-3723
Versions	4.5.0, 4.4.2
Edition	All

Documents how-to upgrade the edition/flavo(u)r of a DXP installation

Checklist

• [ ] Text renders correctly
• [ ] Text has been checked with vale
• [ ] Description metadata is up to date
• [ ] Redirects cover removed/moved pages
• [ ] Code samples are working
• [ ] PHP code samples have been fixed with PHP CS fixer
• [ ] Added link to this PR in relevant JIRA ticket or code PR