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

src/backend/access/heap/heapam.c

@@ -1122,7 +1122,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 	/*
 	 * Set up a read stream for sequential scans and TID range scans. This
 	 * should be done after initscan() because initscan() allocates the
-	 * BufferAccessStrategy object passed to the streaming read API.
+	 * BufferAccessStrategy object passed to the read stream API.
 	 */
 	if (scan->rs_base.rs_flags & SO_TYPE_SEQSCAN ||
 		scan->rs_base.rs_flags & SO_TYPE_TIDRANGESCAN)

src/backend/access/heap/vacuumlazy.c

@@ -13,7 +13,7 @@
  * autovacuum_work_mem) memory space to keep track of dead TIDs.  If the
  * TID store is full, we must call lazy_vacuum to vacuum indexes (and to vacuum
  * the pages that we've pruned). This frees up the memory space dedicated to
- * to store dead TIDs.
+ * store dead TIDs.
  *
  * In practice VACUUM will often complete its initial pass over the target
  * heap relation without ever running out of space to store TIDs.  This means

src/backend/catalog/namespace.c

@@ -108,7 +108,7 @@
  * (if one exists).
  *
  * activeSearchPath is always the actually active path; it points to
- * to baseSearchPath which is the list derived from namespace_search_path.
+ * baseSearchPath which is the list derived from namespace_search_path.
  *
  * If baseSearchPathValid is false, then baseSearchPath (and other derived
  * variables) need to be recomputed from namespace_search_path, or retrieved

src/backend/replication/logical/slotsync.c

@@ -599,7 +599,7 @@ update_and_persist_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid)
  * metadata of the slot as per the data received from the primary server.
  *
  * The slot is created as a temporary slot and stays in the same state until the
- * the remote_slot catches up with locally reserved position and local slot is
+ * remote_slot catches up with locally reserved position and local slot is
  * updated. The slot is then persisted and is considered as sync-ready for
  * periodic syncs.
  *

src/backend/storage/smgr/smgr.c

@@ -244,7 +244,7 @@ smgropen(RelFileLocator rlocator, ProcNumber backend)
 
 /*
  * smgrpin() -- Prevent an SMgrRelation object from being destroyed at end of
- *				of transaction
+ *				transaction
  */
 void
 smgrpin(SMgrRelation reln)