[1.7.X] Fixed #22557 -- ManifestStaticFilesStorage did not cleanup deleted files.

When using ManifestStaticFilesStorage, deleted static files would be
correctly cleaned up by "collectstatic --clear", but the manifest file
would still contain the stale entries.

Thanks to tedtieken for the report

Backport of 3bec38888f6f4ee9245b004fcb9fe15b35cef469 from master.