fix traner.py import error (#10442)

Author: Yancey

python/paddle/fluid/trainer.py

@@ -22,7 +22,7 @@
 
 # optimizer is same as the parameter of Trainer.__init__. Rename it to opt_module
 import optimizer as opt_module
-import distribute_transpiler
+from transpiler import distribute_transpiler
 
 __all__ = [
     'Trainer',