pg_surgery: Fix off-by-one bug with heap offset

pg_surgery: Fix off-by-one bug with heap offset

heap_force_common() declared a boolean array indexed with an
OffsetNumber for a size of MaxHeapTuplesPerPage.  OffsetNumbers are
1-based, so an input TID whose offset number equals MaxHeapTuplesPerPage
wrote one byte past the end of the stack array, crashing the server.

Like heapam_handler.c, this commit changes the array so as it uses a
0-based index, substracting one from the OffsetNumbers.

Reported-by: Wang Yuelin <violin0613@tju.edu.cn>
Reviewed-by: Ashutosh Sharma <ashu.coek88@gmail.com>
Discussion: https://postgr.es/m/20260604002256.40f1fd544@smtp.qiye.163.com
Backpatch-through: 14