Remove unconditional registration of :android_platform for execution. (…

…#456)

This platform is only valid on Linux machines, and breaks the build when
run from Windows or Mac.

The .bazelrc registers it as an execution platform when used with RBE.

examples/android_instrumentation_test/WORKSPACE

@@ -2,8 +2,8 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 android_sdk_repository(
     name = "androidsdk",
+    api_level = 28,
     build_tools_version = "28.0.2",
-    api_level=28,
 )
 
 android_ndk_repository(
@@ -66,11 +66,10 @@ http_archive(
 )
 
 load("@bazel_toolchains//rules:rbe_repo.bzl", "rbe_autoconfig")
+
 # Creates a default toolchain config for RBE.
 # Use this as is if you are using the rbe_ubuntu16_04 container,
 # otherwise refer to RBE docs.
 rbe_autoconfig(name = "buildkite_config")
-rbe_autoconfig(name = "rbe_default")
 
-# RBE support for android_device and android_instrumentation_test on RBE.
-register_execution_platforms(":android_platform")
+rbe_autoconfig(name = "rbe_default")