don't try to update namespaces for inst-fs files
don't try to update namespaces for inst-fs files

in the edge case where the file does not exist in s3, this will break

fixes CNVS-48727
flag = none

test plan: copy a course with an an instfs attachment with an incorrect
namespace

Change-Id: I073ce7f2385da4c6bd8578d1679a2cd628803140
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/232198
Reviewed-by: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
Reviewed-by: Jacob Fugal <f862f167b85d41b225785c70d70808bc7337c1fe@instructure.com>
Reviewed-by: James Williams <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
QA-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
Product-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>

djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms