Fix file_managed table for ds9.txt

The size of this file, ds9.txt. is not tested in a core migration test so the change was not picked up. In order to add a test FileMigrationSetupTrait needs to be modified to handle more that one file. Currently, I don't think that work is necessary because the file migration is tested and no new files are being added to the fixture. Of course the latter one may change but right now I can't think of any open issue that would require that. The problem arose from doing spelling change fixes to the file ds9.txt and that will not happen again because the file only contains, the '*' character.

And just to note that there is an issue to update the fixture, #3219539: Update Drupal 7 migration database fixture which has some activity this week.

That was meant to be a patch.

The file is now 4 bytes so this is correct. There are two references to ds9.txt in the codebase and only one mentions the file size, so there are no other changes to make here.

I think this qualifies as a quick fix.