DOCSP-10068: [Guides] clarify source cluster requirements (#150)

Author: steveren

source/includes/iterate_all.rst

@@ -67,24 +67,23 @@
      - id: java-sync
        content: |
 
-         You can implement a ``com.mongodb.Block`` to print the results
-         of the iteration
+         You can implement a ``java.util.function.Consumer`` to print the
+         results of the iteration
          
          .. code-block:: java
          
-            Block<Document> printBlock = new Block<Document>() {
-                @Override
-                public void apply(final Document document) {
-                    System.out.println(document.toJson());
+            Consumer<Document> printConsumer = new Consumer<Document>() {
+                public void accept(final Document doc) {
+                    System.out.println(doc.toJson());
                 }
             };
          
          Then iterate the cursor for documents, passing the
-         ``printBlock`` as a parameter.
+         ``printConsumer`` as a parameter.
          
          .. code-block:: java
        
-            findIterable.forEach(printBlock);
+            findIterable.forEach(printConsumer);
 
      - id: nodejs
        content: |

source/includes/migration-pr-compose.rst

@@ -18,7 +18,10 @@
 
   If your deployment is currently a standalone instance, you must first
   :manual:`convert it to a replica set </tutorial/convert-standalone-to-replica-set>`.
-  Live migration of data from sharded clusters is not supported.
+  
+  Live migration of data from sharded clusters is not supported. Your destination
+  cluster may be sharded, but your source cluster must be an unsharded replica
+  set.
 
 * (Optional) Enabled authentication on your source deployment.