pgsql: Fix duplicated consecutive words in comments

Fix duplicated consecutive words in comments

Also, fix a comment incorrectly referencing the "streaming read API".
This was renamed to "read stream" shortly before being committed.

Discussion: https://postgr.es/m/CAApHDvq-2Zdqytm_Hf3RmVf0qg5PS9jTFAJ5QTc9xH9pwvwDTA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/310cd8ab386ca44213b62b1c36162110d46bfc7a

Modified Files
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src/backend/access/heap/heapam.c           | 2 +-
src/backend/access/heap/vacuumlazy.c       | 2 +-
src/backend/catalog/namespace.c            | 2 +-
src/backend/replication/logical/slotsync.c | 2 +-
src/backend/storage/smgr/smgr.c            | 2 +-
5 files changed, 5 insertions(+), 5 deletions(-)