Fix method signature of platform_utils.FileDescriptorStreams._create_stream()

Change-Id: Ib80e4ec5e540d97488e7564703ddbcb74350fdfd
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/251836


Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Rostislav Krasny <rostigm@gmail.com>