put_str: Use memcpy instead of strncpy

This fixes a warning from latest gcc.

There is no point in using strncpy here as we
intentionally copy only the string contents without
the terminating NUL. The len is set from strlen().

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/18627)

crypto/property/property_parse.c

@@ -600,7 +600,7 @@ static void put_str(const char *str, char **buf, size_t *remain, size_t *needed)
         len = *remain - 1;
 
     if (len > 0) {
-        strncpy(*buf, str, len);
+        memcpy(*buf, str, len);
         *buf += len;
         *remain -= len;
     }