Bump TMDbLib from 1.7.3-alpha to 1.8.1

Bumps [TMDbLib](https://github.com/LordMike/TMDbLib) from 1.7.3-alpha to 1.8.1.
- [Release notes](https://github.com/LordMike/TMDbLib/releases)
- [Commits](https://github.com/LordMike/TMDbLib/compare/v1.7.3-alpha...v1.8.1)

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

MediaBrowser.Providers/MediaBrowser.Providers.csproj

@@ -22,7 +22,7 @@
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
     <PackageReference Include="OptimizedPriorityQueue" Version="5.0.0" />
     <PackageReference Include="PlaylistsNET" Version="1.1.3" />
-    <PackageReference Include="TMDbLib" Version="1.7.3-alpha" />
+    <PackageReference Include="TMDbLib" Version="1.8.1" />
   </ItemGroup>
 
   <PropertyGroup>