Update notation of configOBUs.

Uses same style as in the Audio Frame OBU.

index.bs

@@ -2010,7 +2010,7 @@ Parsers SHALL ignore these two fields.
 class IAConfigurationBox extends Box('iacb') {
     unsigned int (8) configurationVersion = 1;
     leb128() configOBUs_size;
-    unsigned int (8) configOBUs[];
+    unsigned int (8 x configOBUs_size) configOBUs;
 }
 ```