R1:24a061f84495

Correct an ambiguous regexp in DiffusionRequest

Summary:
See <https://discourse.phabricator-community.org/t/diffusionrequest-regex-error/2057/>.

The intent of `[\d-,]` is "digits, hyphen, and comma" but `[x-y]` means "character range x-y".

Specify `[\d,-]` instead to disambiguate the hyphen as "literal hyphen", not a character range marker.

Test Plan: I can't reproduce the original error as reported, but browsed around Diffusion for a bit.

Reviewers: amckinley, avivey

Reviewed By: avivey…