[COMMITTERS] pgsql: Don't disallow dropping NOT NULL for a list partition key.

Don't disallow dropping NOT NULL for a list partition key.

Range partitioning doesn't support nulls in the partitioning columns,
but list partitioning does.

Amit Langote, per a complaint from Amul Sul

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/e28b1156122f4d48d6f6f7a7f26381ee7af65a91

Modified Files
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src/backend/commands/tablecmds.c          | 22 +++++++++++++---------
src/test/regress/expected/alter_table.out |  4 ++++
src/test/regress/sql/alter_table.sql      |  5 +++++
3 files changed, 22 insertions(+), 9 deletions(-)