close input load user boundary before return

Summary:
coming from https://buildkite.com/dagster/dagster/builds/15941#cb204426-b352-4a79-97ce-328486c4d805

im not sure this will actually fix the issue but cant hurt

Test Plan: bk

Reviewers: dgibson, sandyryza, yuhan

Reviewed By: yuhan

Differential Revision: https://dagster.phacility.com/D5960