Removing version of AspNetCore.All for AppVeyor

Author: jeremydmiller

src/Lamar.AspNetCoreTests/Lamar.AspNetCoreTests.csproj

@@ -8,7 +8,7 @@
     <PackageReference Include="Baseline" Version="1.5.0" />
     <PackageReference Include="IdentityServer4" Version="2.3.0" />
     <PackageReference Include="IdentityServer4.AccessTokenValidation" Version="2.6.0" />
-    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.1.6" />
+    <PackageReference Include="Microsoft.AspNetCore.All"  />
     <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.4" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
     <PackageReference Include="xunit" Version="2.4.1" />