Bump to xamarin/java.interop/master@b991bb86 (#5198)

Fixes: dotnet/java-interop#461
Fixes: dotnet/java-interop#682
Fixes: dotnet/java-interop#717
Fixes: dotnet/java-interop#719
Fixes: dotnet/java-interop#728

Changes: dotnet/java-interop@ac914ce...b991bb8

  * dotnet/java-interop@b991bb86: [generator] Revert change to use auto-properties in EventArgs classes (#736)
  * dotnet/java-interop@ee50d89b: Bump to xamarin/xamarin-android-tools/master@f2af06f2 (#733)
  * dotnet/java-interop@a0b895c1: [build] Suppress NuGet warnings (#730)
  * dotnet/java-interop@8b1b0507: [generator] Fix parsing of complex generic types (#729)
  * dotnet/java-interop@ee7afeed: [generator] Prevent generating duplicate EventArgs classes (#726)
  * dotnet/java-interop@1f21f38c: [generator] Use GC.KeepAlive for reference type method parameters. (#725)
  * dotnet/java-interop@5136ef98: [Xamarin.Android.Tools.Bytecode] Hide Kotlin nested types inside (#723)
  * dotnet/java-interop@53d60513: [jnimarshalmethod-gen] Fix registration on Windows (#721)
  * dotnet/java-interop@5a834d42: [jnimarshalmethod-gen] Avoid creating AppDomains (#720)
  * dotnet/java-interop@a76edb8c: [Xamarin.Android.Tools.ApiXmlAdjuster] Find app.android.IntentService (#718)
  * dotnet/java-interop@6cde0877: [Java.Interop] Emit a reference assembly for Java.Interop.dll (#716)
  * dotnet/java-interop@b858dc59: [generator] Provide line/col numbers for api.xml warnings (#715)
  * dotnet/java-interop@9be92a04: [ci] Don't kick off CI for documentation only changes. (#712)
  * dotnet/java-interop@03c22722: [jnimarshalmethod-gen] Fix type resolution crash (#706)