Fix Windows build error

httplib.h

@@ -16322,8 +16322,10 @@ inline STACK_OF(X509_NAME) *
   X509 *cert = nullptr;
   while ((cert = PEM_read_bio_X509(bio, nullptr, nullptr, nullptr)) !=
          nullptr) {
-    X509_NAME *name = X509_get_subject_name(cert);
-    if (name) { sk_X509_NAME_push(ca_list, X509_NAME_dup(name)); }
+    const X509_NAME *name = X509_get_subject_name(cert);
+    if (name) {
+      sk_X509_NAME_push(ca_list, X509_NAME_dup(const_cast<X509_NAME *>(name)));
+    }
     X509_free(cert);
   }
   BIO_free(bio);