Bump to xamarin-android-api-compatibility/d15-7/9d71e200

Context: #1303

Fixes an [ABI BREAK][0] from b2ca17a:

	<h3>Type Changed: Android.Widget.ListView</h3>
	<p>Modified fields:</p>
	<pre>
	<div data-is-breaking>	public const <span class='removed removed-inline removed-breaking-inline'>int</span> <span class='added '>ChoiceMode</span> ChoiceModeMultiple = 2;
	</div><div data-is-breaking>	public const <span class='removed removed-inline removed-breaking-inline'>int</span> <span class='added '>ChoiceMode</span> ChoiceModeNone = 0;
	</div><div data-is-breaking>	public const <span class='removed removed-inline removed-breaking-inline'>int</span> <span class='added '>ChoiceMode</span> ChoiceModeSingle = 1;
	</div></pre>

The problem is that [xamarin-android-api-compatibility PR #13][ac-13]
is part of PR #1303, but #1303 hasn't been merged yet. As such, it had
no need to be in the xamarin-android-api-compatibility/d15-7 branch.

It has been reverted, thus fixing the above ABI break.

[0]: https://jenkins.mono-project.com/view/Xamarin.Android/job/xamarin-android/876/console
[ac-13]: xamarin/xamarin-android-api-compatibility#13