pgsql: Fix some typos

Fix some typos

Author: Yongtao Huang
Discussion: https://postgr.es/m/CAOe1Go1F99o5JsphtXdDC5bxm7AzetU8q3AxLh4AAVGKu1AzEQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b199eb89c67d737ced55721590f7fc8ff585e837

Modified Files
--------------
src/backend/access/index/indexam.c                                    | 2 +-
src/backend/commands/explain.c                                        | 2 +-
src/backend/replication/logical/worker.c                              | 2 +-
src/backend/utils/activity/wait_event.c                               | 2 +-
src/test/modules/test_ginpostinglist/expected/test_ginpostinglist.out | 2 +-
src/test/modules/test_ginpostinglist/sql/test_ginpostinglist.sql      | 2 +-
6 files changed, 6 insertions(+), 6 deletions(-)