CLI `manifest migrate` command does not remove `docker` property from build manifest when converting to 0.3.0

[krisbitney]

Describe the bug
When running the CLI's polywrap manifest migrate build command to automatically migrate a build manifest to the latest version, the deprecated top-level docker property is not removed. This leads to an exception when attempting to build a project.

Expected behavior
Ideally, we would like migrate to produce a manifest that "just works". The fix is super simple: we just need to make sure the docker property is dropped during migration.

Screenshots / logs
Exception encountered

❌ Failed to load manifest from ./polywrap.build.yaml: Error: Validation errors encountered while sanitizing BuildManifest format 0.3.0
instance is not allowed to have the additional property "docker"
❌ Failed to compile Polywrap: Error: Validation errors encountered while sanitizing BuildManifest format 0.3.0
instance is not allowed to have the additional property "docker"

Manifest after migration

Diff