Revert "Mono.Android.csproj is missing Configuration.Override.props import."

This reverts commit 74ade54.

Mono.Android.csproj doens't need to import
Configuration.Override.props because Configuration.props already
<Import/>s it (when it exists).

See Configuration.props line 3:

	<Import Project="Configuration.Override.props" Condition="Exists('Configuration.Override.props')" />

If Configuration.Override.props isn't being imported through
Configuration.props, we have bigger problems. <Import/>ing it from
Mono.Android.csproj would just be hiding these bigger problems.

Author: jonpryor

src/Mono.Android/Mono.Android.csproj

@@ -10,7 +10,6 @@
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
   </PropertyGroup>
   <Import Project="..\..\Configuration.props" />
-  <Import Project="..\..\Configuration.Override.props" Condition="Exists('..\..\Configuration.Override.props')" />
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
     <DebugType>full</DebugType>
@@ -311,4 +310,4 @@
       <ReferenceOutputAssembly>False</ReferenceOutputAssembly>
     </ProjectReference>
   </ItemGroup>
-</Project>
+</Project>