test/*,cosmetics: normalize void parameter lists

replace (void) with (); use of this synonym is more common in C++ code.

Change-Id: I9813e82234dc9caa7115918a0491b0040f6afaf4
diff --git a/test/md5_helper.h b/test/md5_helper.h
index 9443cb2..69f1ae7 100644
--- a/test/md5_helper.h
+++ b/test/md5_helper.h
@@ -48,7 +48,7 @@
     MD5Update(&md5_, data, static_cast<uint32_t>(size));
   }
 
-  const char *Get(void) {
+  const char *Get() {
     static const char hex[16] = {
       '0', '1', '2', '3', '4', '5', '6', '7',
       '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',