remove comma splice (#388)

Author: jeff-allen-mongo

source/core/wiredtiger.txt

@@ -76,7 +76,7 @@ Starting in MongoDB 5.0, you can use the
 long WiredTiger keeps the snapshot history.
 
 Increasing the value of :parameter:`minSnapshotHistoryWindowInSeconds`
-increases disk usage, because the server must maintain the history of
+increases disk usage because the server must maintain the history of
 older modified values within the specified time window. The amount of
 disk space used depends on your workload, with higher volume workloads
 requiring more disk space.