FIX: don't use etags for post-upload verification (#21923)

They don't work for server-side encryption with customer keys, and so instead we just use Content-MD5 to ensure there was no corruption in transit, which is the best we can do.

See also: https://meta.discourse.org/t/s3-uploads-incompatible-with-server-side-encryption/266853

lib/tasks/uploads.rake

@@ -119,7 +119,6 @@ def create_migration
     s3_options: FileStore::ToS3Migration.s3_options_from_env,
     dry_run: !!ENV["DRY_RUN"],
     migrate_to_multisite: !!ENV["MIGRATE_TO_MULTISITE"],
-    skip_etag_verify: !!ENV["SKIP_ETAG_VERIFY"],
   )
 end