Composer Lint needs to check original composer.json in addition to the modified version

Migrated issue

Reported by: kristiaanvandeneynde

Related to !215 (merged)

Problem/Motivation

Had a trailing comma behind my last requirement, which ended up not loading my dev requirements, yet the composer lint stage went green. It ended up in said dev requirement not being included (phpstan-prophecy), making phpstan really angry about my prophecies.

Steps to reproduce

See these pipelines: flexible_permissions@7ed96f7b

Proposed resolution

No clue, shouldn't this have been caught by composer lint?