[MASSMAIL]pgsql: Remove references to old function name

Remove references to old function name

In a97bbe1f1df I accidentally referenced heapgetpage(), both in a function
name and a comment. But since 44086b09753 the relevant function is named
heap_prepare_pagescan().  Rename the new function to page_collect_tuples().

Reported-by: Melanie Plageman <melanieplageman@gmail.com>
Reported-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/20240407172615.cocrsvboqm3ttqe4@awork3.anarazel.de
Discussion: https://postgr.es/m/CAApHDvp4SniHopTrVeKWcEvNXFtdki0utAvO=5R7H6TNhtULRQ@mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/e3b69be951597eeee9c546fbfc51f9f801c7b198

Modified Files
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src/backend/access/heap/heapam.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)