clarify a typo and a comment

src/main/java/com/google/cloud/discotoproto3converter/proto3/DocumentToProtoConverter.java

@@ -617,7 +617,7 @@ private Field schemaToField(Schema sch, boolean optional, String debugPreviousPa
         if (sch.format() == Format.STRUCT) {
           valueType = Message.PRIMITIVES.get("google.protobuf.Struct");
           this.usesStructProto = true;
-          // `additionalProperties' in the schema further specified the JSON format, but
+          // `additionalProperties' in the schema further specifies the JSON format, but
           // "google.protobuf.Struct" is enough for specifying the proto message field type.
         } else {
           if (sch.additionalProperties() != null) {

src/main/java/com/google/cloud/discotoproto3converter/proto3/Message.java

@@ -38,11 +38,10 @@ public class Message extends ProtoElement<Message> {
     PRIMITIVES.put("double", new Message("double", false, false, null));
     PRIMITIVES.put("", new Message("", false, true, null));
 
-    // This isn't technically a primitive, but it is a fundamental well-known-type with no a priori
-    // structure.
+    // These aren't technically primitives, but they are opaque types we treat as such, essentially.
     //
-    // TODO: If we start accepting additional well-known types, create a specific data structure for
-    // those rather than overloading "PRIMITIVES".
+    // TODO: Consider renaming this field more accurately, or creating a parallel field for these
+    // types.
     PRIMITIVES.put("google.protobuf.Any", new Message("google.protobuf.Any", false, false, null));
     PRIMITIVES.put(
         "google.protobuf.Value", new Message("google.protobuf.Value", false, false, null));