pgsql: Comments and doc fixes for commit 40d964ec99.

Comments and doc fixes for commit 40d964ec99.

Reported-by: Justin Pryzby
Author: Justin Pryzby, with few changes by me
Reviewed-by: Amit Kapila and Sawada Masahiko
Discussion: https://postgr.es/m/20200322021801.GB2563@telsasoft.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a6fea120a7e3858e642bb5e96027f166a1a6f134

Modified Files
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doc/src/sgml/ref/vacuum.sgml          | 22 +++++++--------
src/backend/access/heap/vacuumlazy.c  | 52 +++++++++++++++++------------------
src/backend/access/transam/parallel.c |  2 +-
src/backend/commands/vacuum.c         | 20 +++++++-------
src/include/commands/vacuum.h         |  2 +-
5 files changed, 49 insertions(+), 49 deletions(-)