MAINTAINERS: remove stale kdump project URL

The kdump project URL in MAINTAINERS points to
http://lse.sourceforge.net/kdump/, but it is no longer maintained.

Remove this outdated link to avoid confusion and keep the file
up to date.

Discussion to remove this link:
https://lore.kernel.org/all/e1e9e200-17d7-4ae9-b0eb-71300f4eb1ac@linux.ibm.com/

Link: https://lore.kernel.org/20260418080226.40415-1-sourabhjain@linux.ibm.com
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <baoquan.he@linux.dev>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>