pgsql: Fix typos and grammar of some comments

Fix typos and grammar of some comments

These errors have been reported to the mailing lists in the last few
weeks. Some of the spots fixed have been noticed by myself during
independent code reviews, but not all.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/be00f041a331d5e6a49f21f139c9518542bdf9b3

Modified Files
--------------
contrib/amcheck/verify_heapam.c | 4 ++--
src/backend/access/common/toast_internals.c | 6 +++---
src/backend/access/index/genam.c | 2 +-
src/backend/replication/logical/logicalctl.c | 12 ++++++------
src/bin/pg_ctl/t/001_start_stop.pl | 2 +-
src/include/mb/pg_wchar.h | 2 +-
src/include/utils/rel.h | 2 +-
src/include/varatt.h | 2 +-
src/port/path.c | 2 +-
.../modules/test_extensible/expected/test_extensible.out | 2 +-
src/test/modules/test_extensible/sql/test_extensible.sql | 2 +-
11 files changed, 19 insertions(+), 19 deletions(-)