Bump Fluid.Core from 2.15.0 to 2.16.0 in /src

Bumps [Fluid.Core](https://github.com/sebastienros/fluid) from 2.15.0 to 2.16.0.
- [Release notes](https://github.com/sebastienros/fluid/releases)
- [Commits](sebastienros/fluid@v2.15.0...v2.16.0)

---
updated-dependencies:
- dependency-name: Fluid.Core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

src/Cottle.Benchmark/Cottle.Benchmark.csproj

@@ -15,7 +15,7 @@
   <ItemGroup>
     <PackageReference Include="BenchmarkDotNet" Version="0.14.0" />
     <PackageReference Include="DotLiquid" Version="2.3.0" />
-    <PackageReference Include="Fluid.Core" Version="2.15.0" />
+    <PackageReference Include="Fluid.Core" Version="2.16.0" />
     <PackageReference Include="Mustachio" Version="2.1.0" />
     <PackageReference Include="RazorLight" Version="2.3.1" />
     <PackageReference Include="Scriban" Version="5.12.0" />