Fix a potential misaligned memory access

in test/wpackettest.c:593:18: runtime error: load of misaligned address
for type 'uint64_t', which requires 8 byte alignment.

Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/26269)

(cherry picked from commit 94f95efce9)

test/wpackettest.c

@@ -590,7 +590,7 @@ static int test_WPACKET_quic_vlint_random(void)
         if (!TEST_int_gt(RAND_bytes(rand_data, sizeof(rand_data)), 0))
             return cleanup(&pkt);
 
-        expected = *(uint64_t*)rand_data;
+        memcpy(&expected, rand_data, sizeof(uint64_t));
 
         /*
          * Ensure that all size classes get tested with equal probability.