[javadoc] Fix SerialFormBuilder eliminate String bashing

SerializedFormBuilder.java: needs to be fixed correctly....

            String refSignature = ch.getReferencedSignature(tag);
            // TODO: Print the signature directly, if it is an array, the
            // current DocTree APIs makes it very hard to distinguish
            // an as these are returned back as "Array" a DeclaredType.
            if (refSignature.endsWith("[]")) {
                te = null;
                fieldType = refSignature;
            }