Set minSdkVersion to 16 for AppRTCMobile_stubbed_video_io_test_apk.

After [1], the Chromium Roll into WebRTC fails with the following error:

FAILED: gen/examples/ \
AppRTCMobile_stubbed_video_io_test_apk__apk_manifest/AndroidManifest.xml

uses-sdk:minSdkVersion 13 cannot be smaller than version 14 declared in
library [...]/android_arch_lifecycle_runtime_java/AndroidManifest.xml
as the library might be using APIs not available in 13
	Suggestion: use a compatible library with a minSdk of at most 13,
		or increase this project's minSdk version to at least 14,
		or use tools:overrideLibrary="android.arch.lifecycle" to force
        usage (may lead to runtime failures)

[1] - https://chromium-review.googlesource.com/c/chromium/src/+/1298342

Bug: None
Change-Id: I839dd9dbb346d8f40c25f6a6b93b5d5fc1c26ae9
Reviewed-on: https://webrtc-review.googlesource.com/c/108080
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25381}