DOCS-15063 Replace old query optimizer language (#2379)

* DOCS-15063 replace old optimizer language

* replace more references to optimizer

Author: lindseymoore

source/core/query-plans.txt

@@ -16,7 +16,7 @@ Query Plans
 
 .. TODO Consider moving this to the mechanics of the index section
 
-For a query, the MongoDB query optimizer chooses and caches the most
+For a query, the MongoDB query planner chooses and caches the most
 efficient query plan given the available indexes. The evaluation of the
 most efficient query plan is based on the number of "work units"
 (``works``) performed by the query execution plan when the query planner
@@ -237,10 +237,10 @@ Index Filters
 -------------
 
 Index filters are set with the :dbcommand:`planCacheSetFilter` command
-and determine which indexes the optimizer evaluates for a :term:`query
+and determine which indexes the planner evaluates for a :term:`query
 shape`. A query shape consists of a combination of query, sort, and
 projection specifications. If an index filter exists for a given query
-shape, the optimizer only considers those indexes specified in the
+shape, the planner only considers those indexes specified in the
 filter.
 
 When an index filter exists for the query shape, MongoDB ignores the
@@ -249,15 +249,15 @@ filter for a query shape, check the :data:`~explain.queryPlanner.indexFilterSet`
 field of either the :method:`db.collection.explain()` or the
 :method:`cursor.explain()` method.
 
-Index filters only affect which indexes the optimizer evaluates; the
-optimizer may still select the collection scan as the winning plan for
+Index filters only affect which indexes the planner evaluates; the
+planner may still select the collection scan as the winning plan for
 a given query shape.
 
 Index filters exist for the duration of the server process and do not
 persist after shutdown. MongoDB also provides a command to manually remove
 filters.
 
-Because index filters override the expected behavior of the optimizer
+Because index filters override the expected behavior of the planner
 as well as the :method:`~cursor.hint()` method, use index filters
 sparingly.