Bump altcover from 8.6.14 to 8.6.68 (#287)

Bumps [altcover](https://github.com/SteveGilham/altcover) from 8.6.14 to 8.6.68.
- [Release notes](https://github.com/SteveGilham/altcover/releases)
- [Changelog](https://github.com/SteveGilham/altcover/blob/master/ReleaseNotes.md)
- [Commits](SteveGilham/altcover@release/v8.6.14...release/v8.6.68)

---
updated-dependencies:
- dependency-name: altcover
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Steve Smith <[email protected]>

test/GuardClauses.UnitTests/GuardClauses.UnitTests.csproj

@@ -7,7 +7,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="altcover" Version="8.6.14" />
+        <PackageReference Include="altcover" Version="8.6.68" />
         <PackageReference Include="coverlet.msbuild" Version="3.2.0">
             <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
             <PrivateAssets>all</PrivateAssets>