Remove uses of 'aapt_version' attribute.

Bazel 1.0 [1] enables aapt2 by default, so this attribute doesn't do anything.
Bazel 2.0 [2] will prohibit [3] any uses of this attribute.

This also means that building with Bazel versions <1.0 would potentially use aapt1, but this might actually be a good thing.  TF has a minimum version requirement of 0.19, and many aapt2-related fixes have been made in the 0.2x series.

[1] https://blog.bazel.build/2019/10/10/bazel-1.0.html
[2] https://github.com/bazelbuild/bazel/issues/10000
[3] b3f54f6732/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java (L262)
[4] dc73a9889f/WORKSPACE (L92)

PiperOrigin-RevId: 281679131
Change-Id: I47818b8b59eeb78a8c439523ce72e388428f2da9

tensorflow/examples/android/BUILD

@@ -66,7 +66,6 @@ android_binary(
     srcs = glob([
         "src/**/*.java",
     ]),
-    aapt_version = "aapt2",
     # Package assets from assets dir as well as all model targets. Remove undesired models
     # (and corresponding Activities in source) to reduce APK size.
     assets = [

tensorflow/lite/java/demo/app/src/main/BUILD

@@ -8,7 +8,6 @@ package(
 android_binary(
     name = "TfLiteCameraDemo",
     srcs = glob(["java/**/*.java"]),
-    aapt_version = "aapt2",
     assets = [
         "//tensorflow/lite/java/demo/app/src/main/assets:labels_mobilenet_quant_v1_224.txt",
         "@tflite_mobilenet_quant//:mobilenet_v1_1.0_224_quant.tflite",

tensorflow/lite/java/ovic/demo/app/BUILD

@@ -11,7 +11,6 @@ android_binary(
     srcs = [
         "OvicBenchmarkerActivity.java",
     ],
-    aapt_version = "aapt2",
     assets = [
         "//tensorflow/lite/java/ovic/src/testdata:coco_labels.txt",
         "//tensorflow/lite/java/ovic/src/testdata:labels.txt",

tensorflow/lite/models/smartreply/demo/app/src/main/BUILD

@@ -20,7 +20,6 @@ filegroup(
 android_binary(
     name = "SmartReplyDemo",
     srcs = glob(["java/**/*.java"]),
-    aapt_version = "aapt2",
     assets = [":assets"],
     assets_dir = "",
     custom_package = "com.example.android.smartreply",