pgsql: Fix some grammar and typos in comments and docs

Fix some grammar and typos in comments and docs

The documentation fixes are backpatched down to where they apply.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20201031020801.GD3080@telsasoft.com
Backpatch-through: 9.6

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8a15e735be00f156a7227741c0ce88702e6de099

Modified Files
--------------
contrib/amcheck/verify_heapam.c                  | 4 ++--
contrib/pgcrypto/pgp-compress.c                  | 2 +-
doc/src/sgml/auto-explain.sgml                   | 2 +-
doc/src/sgml/ddl.sgml                            | 2 +-
doc/src/sgml/ref/pg_rewind.sgml                  | 2 +-
src/backend/access/heap/pruneheap.c              | 2 +-
src/backend/catalog/namespace.c                  | 2 +-
src/backend/catalog/pg_namespace.c               | 2 +-
src/backend/commands/copy.c                      | 6 +++---
src/backend/commands/tablecmds.c                 | 2 +-
src/backend/executor/execExpr.c                  | 2 +-
src/backend/executor/nodeIncrementalSort.c       | 2 +-
src/backend/executor/nodeLimit.c                 | 2 +-
src/backend/optimizer/path/allpaths.c            | 2 +-
src/backend/optimizer/plan/analyzejoins.c        | 2 +-
src/backend/partitioning/partbounds.c            | 2 +-
src/backend/postmaster/interrupt.c               | 2 +-
src/backend/statistics/dependencies.c            | 2 +-
src/backend/statistics/extended_stats.c          | 2 +-
src/backend/storage/buffer/bufmgr.c              | 2 +-
src/backend/utils/adt/varlena.c                  | 2 +-
src/bin/pg_rewind/parsexlog.c                    | 2 +-
src/bin/pgbench/pgbench.c                        | 2 +-
src/interfaces/libpq/fe-connect.c                | 2 +-
src/test/modules/dummy_index_am/dummy_index_am.c | 2 +-
25 files changed, 28 insertions(+), 28 deletions(-)