Update logging source generator documentation once generics changes are published

[svick]

Describe the issue or suggestion

dotnet/runtime#124638 will enable usage of generics in logging methods that use the logging source generator. That change should be reflected in the documentation.

These changes are in #51839 and I think they should be merged once the source generator changes are published.

[svick]

Changes from dotnet/runtime#124589 should be reflected in the documentation as well.