Fix memory leak of Ractor basket when sending to closed Ractor

The following script leaks memory:

    r = Ractor.new { }
    r.value

    10.times do
      100_000.times do
        r.send(123)
      rescue Ractor::ClosedError
      end

      puts `ps -o rss= -p #{$$}`
    end

Before:

    18508
    25420
    32460
    40012
    47308
    54092
    61132
    68300
    75724
    83020

After:

    11432
    11432
    11432
    11432
    11432
    11432
    11432
    11432
    11432
    11688

Author: peterzhu2118

ractor_sync.c

@@ -1197,6 +1197,7 @@ ractor_send_basket(rb_execution_context_t *ec, const struct ractor_port *rp, str
         RUBY_DEBUG_LOG("closed:%u@r%u", (unsigned int)ractor_port_id(rp), rb_ractor_id(rp->r));
 
         if (raise_on_error) {
+            ractor_basket_free(b);
             rb_raise(rb_eRactorClosedError, "The port was already closed");
         }
     }