Flow Bugfix Release: 8.3.15, 9.0.2

[lubitz (Denny Lubitz)]

I tagged bugfix releases for Neos.
Thanks to all the contributors who helped with this release <3

• mhsdesign
• Sebobo
• dlubitz

The following fixes are included in the new version 8.3.15 and 9.0.2:

• BUGFIX: Set property to null via objects yaml
• BUGFIX: Accept node names starting with numbers in fizzle parser
• BUGFIX: Replace skip migrations with simple return