DOCS-717 correction

Author: Sam Kleinman

source/reference/command/collMod.txt

@@ -49,5 +49,8 @@ collMod
          as a result of document growth, and *does not* affect
          existing allocations.
 
-         This command obtains a write lock on the affected database
-         and will block other operations until it has completed.
+         .. Commenting out the following after DOCS-717, it does take
+            a lock but its to cover a very small metadata change.
+            
+            This command obtains a write lock on the affected database
+            and will block other operations until it has completed.