Rename heap_replace to heap_update.

src/backend/access/heap/heapam.c

src/backend/catalog/aclchk.c

src/backend/catalog/heap.c

src/backend/catalog/index.c

src/backend/catalog/pg_operator.c

src/backend/catalog/pg_type.c

src/backend/commands/async.c

src/backend/commands/command.c

src/backend/commands/comment.c

src/backend/commands/rename.c

src/backend/commands/trigger.c

src/backend/executor/execMain.c

src/backend/rewrite/rewriteSupport.c

src/backend/utils/adt/sets.c

src/include/access/heapam.h