Fix the generation of collections of documents in protocol tests

smithy-lang/smithy#1097 adds a protocol test for sets of
documents and without this change the generated tests are invalid, as they
are missing the separating commas that other types receive.

Author: adamthom-amzn

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/HttpProtocolTestGenerator.java

@@ -1034,7 +1034,7 @@ public Void numberNode(NumberNode node) {
         public Void objectNode(ObjectNode node) {
             // Short circuit document types, as the direct value is what we want.
             if (workingShape.isDocumentShape()) {
-                writer.writeInline(Node.prettyPrintJson(node));
+                writer.writeInline(Node.prettyPrintJson(node)).writeInline(",");
                 return null;
             }
 
@@ -1256,7 +1256,7 @@ public Void numberNode(NumberNode node) {
         public Void objectNode(ObjectNode node) {
             // Short circuit document types, as the direct value is what we want.
             if (workingShape.isDocumentShape()) {
-                writer.writeInline(Node.prettyPrintJson(node));
+                writer.writeInline(Node.prettyPrintJson(node)).writeInline(",");
                 return null;
             }