Bump Xamarin.AndroidX.Annotation from 1.4.0 to 1.6.0.4

Bumps [Xamarin.AndroidX.Annotation](https://github.com/xamarin/AndroidX) from 1.4.0 to 1.6.0.4.
- [Commits](https://github.com/xamarin/AndroidX/commits)

---
updated-dependencies:
- dependency-name: Xamarin.AndroidX.Annotation
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

ExoPlayer.Common/ExoPlayer.Common.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Xamarin.AndroidX.Annotation" Version="1.4.0" />
+    <PackageReference Include="Xamarin.AndroidX.Annotation" Version="1.6.0.4" />
     <PackageReference Include="Xamarin.Google.Guava" Version="31.1.0.8" />
   </ItemGroup>