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/ssltest_old.c b/test/ssltest_old.c
index 9e3bb7a..b95a5a4 100644
--- a/test/ssltest_old.c
+++ b/test/ssltest_old.c
@@ -25,7 +25,7 @@
 #include <string.h>
 #include <time.h>
 
-#include <internal/nelem.h>
+#include "internal/nelem.h"
 
 #define USE_SOCKETS
 #include "e_os.h"