pgsql: Remove T_Join and T_Plan

Remove T_Join and T_Plan

These are abstract node types that don't need to have a node tag
defined.

Discussion: https://www.postgresql.org/message-id/2592455.1657140387%40sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/251154bebe98ca5d3487ccbe0dceb7f412b57934

Modified Files
--------------
src/backend/nodes/copyfuncs.c                    | 40 ------------------------
src/backend/nodes/outfuncs.c                     | 23 --------------
src/backend/nodes/readfuncs.c                    | 30 ------------------
src/include/catalog/catversion.h                 |  2 +-
src/include/nodes/nodes.h                        |  2 --
src/test/modules/test_oat_hooks/test_oat_hooks.c |  6 ----
6 files changed, 1 insertion(+), 102 deletions(-)