Use predictable filenames when downloading raw diffs from a revision

Summary:
To prevent spammers from abusing this feature on a public server, do not include query parameters in the generated filenames. See https://github.com/mozilla-conduit/phabricator/commit/d8bb7d91b7d219902afed1ae7a8ae5e33862a842.

Ref T15665.

Test Plan: Download raw diff from a revision and check filename in URL.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15665

Differential Revision: https://we.phorge.it/D25478

Signed-off-by: Zero King <l2dy@icloud.com>