Update CODEOWNERS for .NET Architecture Guide (#48870)

Author: gewarren

.github/CODEOWNERS

@@ -55,7 +55,7 @@
 /docs/machine-learning/ @gewarren @luisquintanilla @JakeRadMSFT @dotnet/docs
 
 # The .NET Architecture Guide:
-/docs/architecture/ @nishanil @IEvangelist @dotnet/docs
+/docs/architecture/ @IEvangelist @dotnet/docs
 
 # .NET Orleans
 /docs/orleans/ @IEvangelist @dotnet/docs