vmcoreinfo: Remove documentation of PG_slab and PG_hugetlb

The changes to kernel/vmcore_info.c were sadly not reflected in the
documentation.  Rectify that for both these flags as well as adding
PAGE_UNACCEPTED_MAPCOUNT_VALUE.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Harry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20250611155916.2579160-8-willy@infradead.org


Signed-off-by: Vlastimil Babka <vbabka@suse.cz>