Fix filename (#6623)

* fix TF_OD_API_LABELS_FILE name problem

* Fix variable TF_OD_API_LABELS_FILE in documention

research/object_detection/g3doc/running_on_mobile_tensorflowlite.md

@@ -131,7 +131,7 @@ the
 $TF_EXAMPLES/lite/examples/object_detection/android/app/src/main/java/org/tensorflow/demo/DetectorActivity.java
 file in a text editor and find the definition of TF_OD_API_LABELS_FILE. Update
 this path to point to your new label map file:
-"file:///android_asset/labels_list.txt". Note that if your model is quantized,
+"labels_list.txt". Note that if your model is quantized,
 the flag TF_OD_API_IS_QUANTIZED is set to true, and if your model is floating
 point, the flag TF_OD_API_IS_QUANTIZED is set to false. This new section of
 DetectorActivity.java should now look as follows for a quantized model:
@@ -139,7 +139,7 @@ DetectorActivity.java should now look as follows for a quantized model:
 ```shell
   private static final boolean TF_OD_API_IS_QUANTIZED = true;
   private static final String TF_OD_API_MODEL_FILE = "detect.tflite";
-  private static final String TF_OD_API_LABELS_FILE = "file:///android_asset/labels_list.txt";
+  private static final String TF_OD_API_LABELS_FILE = "labels_list.txt";
 ```
 
 Once you’ve copied the TensorFlow Lite model and edited the gradle build script