Use "" not <> for internal/ includes

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4217)
diff --git a/test/mdc2test.c b/test/mdc2test.c
index 5dfe60e..0658843 100644
--- a/test/mdc2test.c
+++ b/test/mdc2test.c
@@ -9,7 +9,7 @@
 
 #include <string.h>
 
-#include <internal/nelem.h>
+#include "internal/nelem.h"
 #include "testutil.h"
 
 #if defined(OPENSSL_NO_DES) && !defined(OPENSSL_NO_MDC2)