Remove Microsoft.CodeAnalysis.CSharp.Analyzer.Testing (#102)

Remove `Microsoft.CodeAnalysis.CSharp.Analyzer.Testing` because it is
duplicative with `Microsoft.CodeAnalysis.CSharp.CodeFix.Testing`. This
is common when building analyzers that contain code fixes. From a
testing perspective, an analyzer test is just a code fix test with an
"empty" or "null pattern" code fixer.

This also unblocks #97, as the two packages otherwise need upgrading
together. However, cleaning up our dependencies is preferred to creating
a group in dependabot.

Source/Moq.Analyzers.Test/Moq.Analyzers.Test.csproj

@@ -19,7 +19,6 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Analyzer.Testing" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp.CodeFix.Testing" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" />
     <PackageReference Include="Verify.Nupkg" />

build/targets/tests/Packages.props

@@ -1,7 +1,6 @@
 <Project>
   <ItemGroup>
     <PackageVersion Include="ReportGenerator" Version="5.3.6" />
-    <PackageVersion Include="Microsoft.CodeAnalysis.CSharp.Analyzer.Testing" Version="1.1.2-beta1.24273.1" />
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp.CodeFix.Testing" Version="1.1.2-beta1.24273.1" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
     <PackageVersion Include="Verify.Nupkg" Version="1.1.5" />