openssl: fix "Value stored to 'rc' is never read" scan-build error

lib/vtls/openssl.c

@@ -3067,12 +3067,12 @@ static CURLcode servercert(struct connectdata *conn,
   ASN1_TIME_print(mem, X509_get0_notBefore(BACKEND->server_cert));
   len = BIO_get_mem_data(mem, (char **) &ptr);
   infof(data, " start date: %.*s\n", len, ptr);
-  rc = BIO_reset(mem);
+  (void)BIO_reset(mem);
 
   ASN1_TIME_print(mem, X509_get0_notAfter(BACKEND->server_cert));
   len = BIO_get_mem_data(mem, (char **) &ptr);
   infof(data, " expire date: %.*s\n", len, ptr);
-  rc = BIO_reset(mem);
+  (void)BIO_reset(mem);
 
   BIO_free(mem);