net/rubygem-ovirt-engine-sdk: Fix build with Clang 16 and remove the workaround

ov_http_client.c:1001:47: error: incompatible function pointer types passing 'int (VALUE, VALUE, struct curl_slist )' (aka 'int (unsigned long, unsigned long, struct curl_slist )') to parameter of type 'int (*)(VALUE, VALUE, VALUE)' (aka 'int (*)(unsigned long, unsigned long, unsigned long)') [-Wincompatible-function-pointer-types]

rb_hash_foreach(request_ptr->headers, ov_http_client_add_header, (VALUE) headers);
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~

/usr/local/include/ruby-3.1/ruby/internal/intern/hash.h:83:40: note: passing argument to parameter 'func' here
void rb_hash_foreach(VALUE hash, int (*func)(VALUE key, VALUE val, VALUE arg), VALUE arg);

^

9 warnings and 1 error generated.