pgsql: Reformat some node comments

Reformat some node comments

Reformat some comments in node field definitions to avoid long lines.

This makes room for per-field annotations in a future patch to
generate node support functions automatically.

Discussion: https://www.postgresql.org/message-id/c5906b07-220a-a3d4-8ff3-8ee593009424@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/835d476fd21bcfb60b055941dee8c3d9559af14c

Modified Files
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src/include/nodes/parsenodes.h |   3 +-
src/include/nodes/pathnodes.h  | 686 +++++++++++++++++++++++++++--------------
src/include/nodes/plannodes.h  | 423 ++++++++++++++++++-------
src/include/nodes/primnodes.h  | 240 ++++++++++----
4 files changed, 952 insertions(+), 400 deletions(-)