Add missing "of", change "architecture" to "architectural"

Author: matthurne

source/applications/aggregation.txt

@@ -240,7 +240,7 @@ Sharded Operation
    Some aggregation operations using :dbcommand:`aggregate` will
    cause :program:`mongos` instances to require more CPU resources
    than in previous versions. This modified performance profile may
-   dictate alternate architecture decisions if you make use the
+   dictate alternate architectural decisions if you make use of the
    :term:`aggregation framework` extensively in a sharded environment.
 
 The aggregation framework is compatible with sharded collections.