Remove GitVersionTask from specs projects

Remove GitVersionTask from specs projects.  The specs assemblies are not packaged/published, so don't (strictly) need version-stamping.  The namespacing pattern chosen for specs is tripping GitVersionTask only in .NET4.0.

Author: reisenberger

src/Polly.Caching.MemoryCache.Net40Async.Specs/Polly.Caching.MemoryCache.Net40Async.Specs.csproj

@@ -26,7 +26,6 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="FluentAssertions" Version="4.17.0" />
-    <PackageReference Include="GitVersionTask" Version="3.1.2" />
     <PackageReference Include="Microsoft.Bcl" Version="1.1.10" />
     <PackageReference Include="Microsoft.Bcl.Async" Version="1.0.168" />
     <PackageReference Include="Microsoft.Bcl.Build" Version="1.0.21" />

src/Polly.Caching.MemoryCache.Net45.Specs/Polly.Caching.MemoryCache.Net45.Specs.csproj

@@ -29,7 +29,6 @@
   <ItemGroup>
     <PackageReference Include="Polly" Version="5.9.0" />
     <PackageReference Include="FluentAssertions" Version="4.17.0" />
-    <PackageReference Include="GitVersionTask" Version="3.1.2" />
     <PackageReference Include="xunit" Version="2.1.0" />
     <PackageReference Include="xunit.extensibility.execution" Version="2.1.0" />
   </ItemGroup>