graphics/libjxl: unbreak fetch via local copy

Index abbreviation in git-format-patch(1) output seems to change
frequently, probably due to GitHub load balancing.

$ make checksum TRYBROKEN= MASTER_SITE_BACKUP= DISTDIR=$(mktemp -dt distfiles)

> License BSD3CLAUSE accepted by the user

> libjxl-0.11.1_1 depends on file: /usr/local/sbin/pkg - found

> d2411cebb0c3.patch doesn't seem to exist in /tmp/distfiles.oqai7utRVB/.

> Attempting to fetch https://github.com/libjxl/libjxl/commit/d2411cebb0c3.patch

fetch: https://github.com/libjxl/libjxl/commit/d2411cebb0c3.patch: size mismatch: expected 3857, actual 3853

> Couldn't fetch it - please try to retrieve this

> port manually into /tmp/distfiles.oqai7utRVB/ and try again.

• Error code 1

Reported by: pkg-fallout (beefy21)