fix conflicting start-after and end-before (#333)

Author: jordan-smith721

source/fundamentals/builders/aggregates.txt

@@ -45,8 +45,8 @@ Use these methods to construct pipeline stages and specify them in your
 aggregation as a list:
 
 .. literalinclude:: /includes/fundamentals/code-snippets/builders/AggBuilders.java
-   :start-after: begin sampleAggregation
-   :end-before: end sampleAggregation
+   :start-after: begin aggregationSample
+   :end-before: end aggregationSample
    :language: java
    :dedent:
 

source/includes/fundamentals/code-snippets/builders/AggBuilders.java

@@ -82,11 +82,11 @@ public static void main(String[] args) {
     }
 
     private void aggregationExample() {
-        // begin sampleAggregation
+        // begin aggregationSample
         Bson matchStage = match(eq("some_field", "some_criteria"));
         Bson sortByCountStage = sortByCount("some_field");
         collection.aggregate(asList(matchStage, sortByCountStage)).forEach(doc -> System.out.println(doc));
-        // end sampleAggregation
+        // end aggregationSample
     }
 
     private void setWindowFieldsStage() {