fix(vim.system): close check handle (#24270)

Fix hang after running vim.system() with sanitizers.

runtime/lua/vim/_system.lua

@@ -287,6 +287,7 @@ function M.run(cmd, opts, on_exit)
         end
       end
       check:stop()
+      check:close()
 
       state.done = true
       state.result = {