Add missing word "command", remove unnecessary comma

Author: matthurne

source/applications/aggregation.txt

@@ -277,7 +277,7 @@ the following limitations:
 
 - Output from the :term:`pipeline` can only contain 16 megabytes. If
   your result set exceeds this limit, the :dbcommand:`aggregate`
-  produces an error.
+  command produces an error.
 
 - If any single aggregation operation consumes more than 10 percent of
-  system RAM, the operation will produce an error.
+  system RAM the operation will produce an error.