Update Placeholder Links (#10018)

* Update 9.0.8.md

* Update 9.0.8.md

* Update 8.0.19.md

Author: victorisr

release-notes/8.0/8.0.19/8.0.19.md

@@ -58,7 +58,7 @@ You need [Visual Studio 17.10](https://visualstudio.microsoft.com) or later to u
 
 ## Feedback
 
-Your feedback is important and appreciated. We've created an issue at [dotnet/core #xxxx](https://github.com/dotnet/core/issues/xxxx) for your questions and comments.
+Your feedback is important and appreciated. We've created an issue at [dotnet/core #10017](https://github.com/dotnet/core/issues/10017) for your questions and comments.
 
 [8.0.413]: 8.0.19.md
 [8.0.316]: 8.0.316.md

release-notes/9.0/9.0.8/9.0.8.md

@@ -57,7 +57,7 @@ You need [Visual Studio 17.12](https://visualstudio.microsoft.com) or later to u
 
 ## Feedback
 
-Your feedback is important and appreciated. We've created an issue at [dotnet/core #xxxx](https://github.com/dotnet/core/issues/xxxx) for your questions and comments.
+Your feedback is important and appreciated. We've created an issue at [dotnet/core #10017](https://github.com/dotnet/core/issues/10017) for your questions and comments.
 
 [9.0.304]: 9.0.8.md
 [9.0.109]: 9.0.109.md