fix: just schemagen improved with explicit yarn install step

[superlinkx]

Description

Changes just schemagen to run a yarn install before attempting to run yarn format

Motivation and Context

just schemagen relies on node_modules to exist locally for yarn format and this can cause issues for downstream workspaces. This adds a local yarn install before attempting to run yarn format to keep things sane

How Has This Been Tested?

Ran just schemagen which not only worked when no node_modules folder existed, but also fixed some formatting we missed before.

Types of changes

• Chore (a change that does not modify the application functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Documentation updates are needed, and have been made accordingly.
• I have added and/or updated tests to cover my changes.
• All new and existing tests passed.
• My changes include a database migration.

[sircodemane]

lgtm