remove almost duplicate, but faulty, readonly check

The writability of the status is already checked at the attribute level

app/contracts/work_packages/base_contract.rb

@@ -136,7 +136,7 @@ module WorkPackages
       ret = super
 
       # If we're in a readonly status and did not move into that status right now
-      # only allow other status transitions
+      # only allow other status transitions. But also prevent that if the associated version is closed.
       if model.readonly_status? && !model.status_id_change
         ret &= %w(status status_id)
       end

lib/api/v3/work_packages/schema/base_work_package_schema.rb

@@ -55,9 +55,6 @@ module API
           def writable?(property)
             property = property.to_sym
 
-            # Special case for readonly: Only status is allowed
-            return property == :status if readonly?
-
             # Special case for milestones + date property
             property = :start_date if property == :date && milestone?
 

spec/lib/api/v3/work_packages/schema/specific_work_package_schema_spec.rb

@@ -92,9 +92,11 @@ describe ::API::V3::WorkPackages::Schema::SpecificWorkPackageSchema do
         .to receive(:readonly_status?)
         .and_return(false)
 
-      is_expected.to_not be_readonly
-      expect(subject.writable?(:status)).to be_truthy
-      expect(subject.writable?(:subject)).to be_truthy
+      # As the writability is memoized we need to have a new schema
+      new_schema = described_class.new(work_package: work_package)
+      expect(new_schema).to_not be_readonly
+      expect(new_schema.writable?(:status)).to be_truthy
+      expect(new_schema.writable?(:subject)).to be_truthy
     end
   end