Fix import in sys_sync example

Author: r41k0u

examples/sys_sync.py

@@ -1,5 +1,5 @@
 from pythonbpf import bpf, map, section, bpfglobal, compile
-from pythonbpf.helper.helpers import ktime
+from pythonbpf.helpers import ktime
 from pythonbpf.maps import HashMap
 
 from ctypes import c_void_p, c_int64, c_uint64