fix: bump DockerPackage buildProcessVersion for OCI layout format change

Increment DockerPackage buildProcessVersion from 3 to 4 to invalidate
existing package hashes when the cache format changes from docker save
to OCI layout.

This prevents old/new leeway versions from conflicting over the cache
format and ensures clean cache invalidation when upgrading.

Co-authored-by: Ona <no-reply@ona.com>

Author: leodido

pkg/leeway/build.go

@@ -114,7 +114,7 @@ const (
 var buildProcessVersions = map[PackageType]int{
 	YarnPackage:    7,
 	GoPackage:      2,
-	DockerPackage:  3,
+	DockerPackage:  4, // Bumped for OCI layout format change (PR #286)
 	GenericPackage: 1,
 }