Fixes: https://github.com/xamarin/xamarin-android/issues/3132
Context: b9349491a1
`Xamarin.Android.Cecil.dll` was created to avoid potential conflicts
and versioning issues with the copy of Cecil that Xamarin Studio was
using at the time; from April 2013:
> The issue is that when Xamarin Studio builds MSBuild-based
> projects, it does so through an intermediary
> `MonoDevelop.Projects.Formats.MSBuild.exe` process, which is
> responsible for using the `Microsoft.Build.*` assemblies to
> actually build the project.
>
> The problem is that the directory containing
> `MonoDevelop.Projects.Formats.MSBuild.exe` --
> `/Applications/Xamarin Studio.app/Contents/MacOS/lib/monodevelop/bin`
> -- contains its own copy of `Mono.Cecil.dll`, and _that_ is the
> version that was used!
>
> Meaning that in order to fix a Xamarin.Android bug, we would need
> an updated Xamarin Studio release.
Considering our migration to .NET, and how infrequently we change our
`Mono.Cecil` reference these days, these potential issues are likely
no longer a concern.
Our unique `Xamarin.Android.Cecil.dll` copy has been removed in favor
of `Mono.Cecil` package references in all projects that depend on it.
8f338230ec