Bump Hangfire.Core from 1.8.3 to 1.8.4 (#1956)

Bumps [Hangfire.Core](https://github.com/HangfireIO/Hangfire) from 1.8.3 to 1.8.4.
- [Release notes](https://github.com/HangfireIO/Hangfire/releases)
- [Commits](HangfireIO/Hangfire@v1.8.3...v1.8.4)

---
updated-dependencies:
- dependency-name: Hangfire.Core
  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>

src/HealthChecks.Hangfire/HealthChecks.Hangfire.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Hangfire.Core" Version="1.8.3" />
+    <PackageReference Include="Hangfire.Core" Version="1.8.4" />
     <PackageReference Include="Microsoft.Extensions.Diagnostics.HealthChecks" Version="7.0.9" />
     <Compile Include="../HealthCheckResultTask.cs" />
   </ItemGroup>