Bump FluentAssertions to 8.6.0

---
updated-dependencies:
- dependency-name: FluentAssertions
  dependency-version: 8.6.0
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: FluentAssertions
  dependency-version: 8.6.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

BitFaster.Caching.UnitTests.Std/BitFaster.Caching.UnitTests.Std.csproj

@@ -10,7 +10,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="FluentAssertions" Version="7.0.0" />
+    <PackageReference Include="FluentAssertions" Version="8.6.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
     <PackageReference Include="Moq" Version="4.20.72" />
     <PackageReference Include="ObjectLayoutInspector" Version="0.1.4" />

BitFaster.Caching.UnitTests/BitFaster.Caching.UnitTests.csproj

@@ -10,7 +10,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="FluentAssertions" Version="7.0.0" />
+    <PackageReference Include="FluentAssertions" Version="8.6.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
     <PackageReference Include="Moq" Version="4.20.72" />
     <PackageReference Include="ObjectLayoutInspector" Version="0.1.4" />