Remove need for pfx from Sample App

Microsoft.Toolkit.Sample.UWP.App/Microsoft.Toolkit.Sample.UWP.App.csproj

@@ -18,7 +18,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <WindowsXamlEnableOverview>true</WindowsXamlEnableOverview>
-    <PackageCertificateKeyFile>Microsoft.Toolkit.Sample.UWP.App_TemporaryKey.pfx</PackageCertificateKeyFile>
+    <AppxPackageSigningEnabled>false</AppxPackageSigningEnabled>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
     <DebugSymbols>true</DebugSymbols>
@@ -132,7 +132,6 @@
     <AppxManifest Include="Package.appxmanifest">
       <SubType>Designer</SubType>
     </AppxManifest>
-    <None Include="Microsoft.Toolkit.Sample.UWP.App_TemporaryKey.pfx" />
   </ItemGroup>
   <ItemGroup>
     <Content Include="Properties\Default.rd.xml" />