Update README.md

`tf.mul` -> `tf.multiply`

inception/inception/slim/README.md

@@ -319,7 +319,7 @@ their use, consider the following example.
 def MyNewOp(inputs):
   varA = ...
   varB = ...
-  outputs = tf.mul(varA, inputs) + varB
+  outputs = tf.multiply(varA, inputs) + varB
   return outputs
 
 ```