fix: Set package.json version to 5.5.0 (re-sync with stable)

[hydrosquall]

Motivation

• chore(release): bump package.json version to v5.6.0 #8378 bumped us 1 patch version too high.
• There may be a longer term fix, but at minimum we should clean up next so that this versioning issue doesn't block the release of core graphing features.

Changes

• Learned from [DRAFT] fix(build): syncback auto-generated version bump from stable back to the main development branch #8380 that we can't fix things by merging stable back into next since that creates a merge conflict. It seems that stable must lead in front of next, the reverse isn't possible.

Testing

• After this merges, the 5.6.0 release PR (Release 5.6.0 #8368 ) should no longer have a merge conflict.

[vega-org-bot]

🚀 PR was released in v5.6.0 🚀