pgsql: Skip bogus find_composite_type_dependencies() call on sequences

Skip bogus find_composite_type_dependencies() call on sequences

A sequence has no rowtype. We called
find_composite_type_dependencies() with InvalidOid, which is harmless
but pointless. Skip it.

This started to happen with commit 344d62fb9a97 in v15, which added
the ALTER SEQUENCE ... SET LOGGED/UNLOGGED subcommand. Before that,
sequences were never rewritten. While this is harmless, backpatch to
keep the code the same on all branches, to make backpatching future
patches a little easier.

Backpatch-through: 15

Branch
------
REL_16_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/70fc6c4b28dff8c3b1ff06c3b3509622b9d97764

Modified Files
--------------
src/backend/commands/tablecmds.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)