Bump Discord.Net from 3.7.2 to 3.8.1

Bumps [Discord.Net](https://github.com/discord-net/Discord.Net) from 3.7.2 to 3.8.1.
- [Release notes](https://github.com/discord-net/Discord.Net/releases)
- [Changelog](https://github.com/discord-net/Discord.Net/blob/dev/CHANGELOG.md)
- [Commits](discord-net/Discord.Net@3.7.2...3.8.1)

---
updated-dependencies:
- dependency-name: Discord.Net
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

TabletBot.Discord/TabletBot.Discord.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Discord.Net" Version="3.7.2" />
+    <PackageReference Include="Discord.Net" Version="3.8.1" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
     <PackageReference Include="Octokit" Version="0.51.0" />
   </ItemGroup>