Docs 14980 remove unsharded from lookup (#127)

* remove unshard verbiage from lookup page

* *

* Add blurb to lookup.txt

* moved starting in mongo5.1 to bottom

Author: ianf-mongodb

source/reference/operator/aggregation/graphLookup.txt

@@ -10,13 +10,13 @@ $graphLookup (aggregation)
    :depth: 1
    :class: singlecol
 
-.. versionchanged:: 3.4
-
 Definition
 ----------
 
 .. pipeline:: $graphLookup
 
+   .. versionchanged:: 5.1
+
    Performs a recursive search on a collection, with options for
    restricting the search by recursion depth and query filter.
 

source/reference/operator/aggregation/lookup.txt

@@ -15,15 +15,18 @@ Definition
 
 .. pipeline:: $lookup
 
-   .. versionchanged:: 5.0
+   .. versionchanged:: 5.1
 
-   Performs a left outer join to an unsharded collection in the *same*
+   Performs a left outer join to a collection in the *same*
    database to filter in documents from the "joined" collection for
    processing. To each input document, the :pipeline:`$lookup` stage
    adds a new array field whose elements are the matching documents
    from the "joined" collection. The :pipeline:`$lookup` stage passes
    these reshaped documents to the next stage.
 
+   Starting in MongoDB 5.1, :pipeline:`$lookup` works across sharded 
+   collections. 
+
 Syntax
 ------