Bump System.Runtime.Caching from 7.0.0 to 8.0.0 (#505)

Bumps [System.Runtime.Caching](https://github.com/dotnet/runtime) from 7.0.0 to 8.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v7.0.0...v8.0.0)

---
updated-dependencies:
- dependency-name: System.Runtime.Caching
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

BitFaster.Caching.Benchmarks/BitFaster.Caching.Benchmarks.csproj

@@ -23,7 +23,7 @@
     <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.13.10" />
     <PackageReference Include="MathNet.Numerics" Version="5.0.0" />
     <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="8.0.0" />
-    <PackageReference Include="System.Runtime.Caching" Version="7.0.0" />
+    <PackageReference Include="System.Runtime.Caching" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup>