[Mono.Android] Remove AdditionalProperties from Java.Interop tools project references.

[jpobst]

Context: e2854ee

Often when compiling XA locally on Windows I get this error:

CSC : error CS2012: Cannot open 'c:\code\xamarin-android\external\Java.Interop\tools\generator\obj\Debug-net7.0\generat
or.dll' for writing -- 'The process cannot access the file 'c:\code\xamarin-android\external\Java.Interop\tools\generat
or\obj\Debug-net7.0\generator.dll' because it is being used by another process.' [c:\code\xamarin-android\external\Java
.Interop\tools\generator\generator.csproj]

This is caused by our usage of AdditionalProperties in our <ProjectReference>. This was needed as a result of trying to reference a net472;net7.0generator project in a MonoAndroid1.0;net7.0Mono.Android project. AdditionalProperties cause an additional build of the referenced project, setting global properties. Both this additional build and the original build are now net7.0 causing them to clobber each other.

Since we're now in a fully .NET world, we are no longer multi-targeting generator or Mono.Android so we can remove this hack and avoid the extra builds and potential sharing violation errors.