Use temporary instead of public files for redirect list export

Problem/Motivation

On S3 there are still issues downloading the export report of path redirects.

Steps to reproduce

When using S3, the public:// download doesn't work uniformly. Changing to temporary:// fixes the path redirect export download.

Proposed resolution

Use temporary:// instead. This doesn't break anything and bypasses S3 when sites happen to use it. There's also no need to use public files, this file should be temporary since it is a one time download.

Remaining tasks

Review this simple patch and merge it.

User interface changes

None.

API changes

None.

Data model changes

None.