Bump Elastic.CommonSchema.Serilog from 8.11.1 to 8.12.1

Bumps [Elastic.CommonSchema.Serilog](https://github.com/elastic/ecs-dotnet) from 8.11.1 to 8.12.1.
- [Release notes](https://github.com/elastic/ecs-dotnet/releases)
- [Commits](elastic/ecs-dotnet@8.11.1...8.12.1)

---
updated-dependencies:
- dependency-name: Elastic.CommonSchema.Serilog
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

src/Tgstation.Server.Host/Tgstation.Server.Host.csproj

@@ -97,7 +97,7 @@
     <!-- Usage: .env file parsing -->
     <PackageReference Include="DotEnv.Core" Version="3.1.0" />
     <!-- Usage: Text formatter for Elasticsearch logging plugin -->
-    <PackageReference Include="Elastic.CommonSchema.Serilog" Version="8.11.1" />
+    <PackageReference Include="Elastic.CommonSchema.Serilog" Version="8.12.1" />
     <!-- Usage: GitLab interop -->
     <PackageReference Include="GitLabApiClient" Version="1.8.0" />
     <!-- Usage: GraphQL API Engine -->