build(deps): bump NLog from 4.7.12 to 4.7.13 in /src (#836)

Bumps [NLog](https://github.com/NLog/NLog) from 4.7.12 to 4.7.13.
- [Release notes](https://github.com/NLog/NLog/releases)
- [Changelog](https://github.com/NLog/NLog/blob/dev/CHANGELOG.md)
- [Commits](NLog/NLog@v4.7.12...v4.7.13)

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

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

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

src/Splat.NLog/Splat.NLog.csproj

@@ -11,7 +11,7 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="NLog" Version="4.7.12" />
+    <PackageReference Include="NLog" Version="4.7.13" />
     <PackageReference Include="System.Collections.Immutable" Version="6.0.0" />
   </ItemGroup>
   <ItemGroup>