pgsql: Fix incorrect and inconsistent comments in tableam.h and heapam.

Fix incorrect and inconsistent comments in tableam.h and heapam.c.

This commit corrects several issues in function comments:

* The parameter "rel" was incorrectly referred to as "relation" in the comments
for table_tuple_delete(), table_tuple_update(), and table_tuple_lock().
* In table_tuple_delete(), "changingPart" was listed as an output parameter
in the comments but is actually input.
* In table_tuple_update(), "slot" was listed as an input parameter
in the comments but is actually output.
* The comment for "update_indexes" in table_tuple_update() was mis-indented.
* The comments for heap_lock_tuple() incorrectly referenced a non-existent
"tid" parameter.

Author: Chao Li <lic(at)highgo(dot)com>
Reviewed-by: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAEoWx2nB6Ay8g=KEn7L3qbYX_4+sLk9XOMkV0XZqHR4cTY8ZvQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7fcb32ad023a434e07b7214c1c762ecd410b6969

Modified Files
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src/backend/access/heap/heapam.c | 1 -
src/include/access/tableam.h | 16 +++++++++-------
2 files changed, 9 insertions(+), 8 deletions(-)